1 00:00:02,090 --> 00:00:03,340 Now at this point, 2 00:00:03,340 --> 00:00:05,760 you know what the web is and how it works 3 00:00:05,760 --> 00:00:08,630 and which key technologies are involved. 4 00:00:08,630 --> 00:00:12,750 I, now, briefly wanna come back to this URL thing here, 5 00:00:12,750 --> 00:00:15,820 the address which you enter in the browser, 6 00:00:15,820 --> 00:00:19,220 and have a look at a couple of other technical details 7 00:00:19,220 --> 00:00:20,590 of how the web works. 8 00:00:20,590 --> 00:00:21,820 And then after that, 9 00:00:21,820 --> 00:00:23,930 we're going to learn how you can get the most out 10 00:00:23,930 --> 00:00:27,100 of the course before we, then, dive right into the code 11 00:00:27,100 --> 00:00:30,760 and you'll learn how to build websites step-by-step. 12 00:00:30,760 --> 00:00:31,920 So let's take another look 13 00:00:31,920 --> 00:00:34,800 at this URL thing now, because there are a couple 14 00:00:34,800 --> 00:00:37,360 of terms you must be aware of. 15 00:00:37,360 --> 00:00:41,300 For example, we have this part at the beginning, here. 16 00:00:41,300 --> 00:00:44,630 You don't enter this on your own very often. 17 00:00:44,630 --> 00:00:47,360 Instead, it's added automatically by browsers. 18 00:00:47,360 --> 00:00:50,120 This defines the so-called protocol that's used 19 00:00:50,120 --> 00:00:52,810 for talking to the remote computer, 20 00:00:52,810 --> 00:00:57,300 to the server. And here, HTTP or HTTPS is the standard. 21 00:00:57,300 --> 00:00:58,520 And as a web developer, 22 00:00:58,520 --> 00:01:00,860 you don't need to worry too much about this 23 00:01:00,860 --> 00:01:04,260 because it is basically handled for you. 24 00:01:04,260 --> 00:01:06,630 Still, that's this part. 25 00:01:06,630 --> 00:01:09,700 Then, we have this thing in the middle. 26 00:01:09,700 --> 00:01:12,160 This is the so-called Domain. 27 00:01:12,160 --> 00:01:14,600 It's the human-readable address, 28 00:01:14,600 --> 00:01:17,970 the identifier of a website. A human-readable 29 00:01:17,970 --> 00:01:21,020 because domains like apple.com, amazon.com, 30 00:01:21,020 --> 00:01:22,460 and so on, of course, 31 00:01:22,460 --> 00:01:25,140 are pretty straight forward to memorize. 32 00:01:25,140 --> 00:01:28,150 And I'll come back to this domain in a couple of seconds, 33 00:01:28,150 --> 00:01:32,420 but this is all the part of every URL that you enter. 34 00:01:32,420 --> 00:01:35,710 Now here, on this example slide, the last part, however, 35 00:01:35,710 --> 00:01:38,640 is not part of every URL. 36 00:01:38,640 --> 00:01:40,390 This is a so-called Path, 37 00:01:40,390 --> 00:01:43,870 and you will often see this in URLs, as well. 38 00:01:43,870 --> 00:01:47,870 Paths act as pointers to specific resources, 39 00:01:47,870 --> 00:01:51,510 specific pages on a website. For example, 40 00:01:51,510 --> 00:01:54,740 if you visit academind.com, which is our website, 41 00:01:54,740 --> 00:01:56,950 if you just enter academind.com, 42 00:01:56,950 --> 00:01:58,930 you end up on the starting page. 43 00:01:58,930 --> 00:02:01,200 But if you, then, go to one of our sub pages, 44 00:02:01,200 --> 00:02:02,800 like the tutorials page, 45 00:02:02,800 --> 00:02:05,130 you see that the address changed. 46 00:02:05,130 --> 00:02:08,350 It's now academind.com/tutorials, 47 00:02:08,350 --> 00:02:11,690 and URL's support paths 48 00:02:11,690 --> 00:02:14,820 because you can now grab the entire URL 49 00:02:14,820 --> 00:02:16,200 that includes the path. 50 00:02:16,200 --> 00:02:18,960 And you could share this with anyone in the world 51 00:02:18,960 --> 00:02:22,080 and if another person enters this same URL 52 00:02:22,080 --> 00:02:26,120 in their browser, they are directed to the same page 53 00:02:26,120 --> 00:02:28,920 on the website, instead of always ending up 54 00:02:28,920 --> 00:02:30,520 on the starting page. 55 00:02:30,520 --> 00:02:32,520 That's why this is another important feature 56 00:02:32,520 --> 00:02:34,510 of the web and of URLs. 57 00:02:34,510 --> 00:02:38,420 You can point at specific resources on a website. 58 00:02:38,420 --> 00:02:39,850 And, of course, in this course, 59 00:02:39,850 --> 00:02:41,770 we're also going to build websites 60 00:02:41,770 --> 00:02:43,973 that consist of multiple pages. 61 00:02:44,900 --> 00:02:46,800 So that's the URL. 62 00:02:46,800 --> 00:02:49,350 Now, I want to come back to this big picture 63 00:02:49,350 --> 00:02:51,610 of how the web works 64 00:02:51,610 --> 00:02:55,480 because here, we now also can dig a little bit deeper 65 00:02:55,480 --> 00:02:59,710 to understand better what exactly happens under the hood 66 00:02:59,710 --> 00:03:02,810 when you enter an address like academind.com 67 00:03:02,810 --> 00:03:06,530 or amazon.com or any other address. 68 00:03:06,530 --> 00:03:07,950 You enter this address, 69 00:03:07,950 --> 00:03:10,600 and we learned that this is called a domain here 70 00:03:10,600 --> 00:03:13,300 if you just have something like academind.com, 71 00:03:13,300 --> 00:03:16,080 and this, then, in the end, leads to the browser 72 00:03:16,080 --> 00:03:18,460 sending a request to some server, 73 00:03:18,460 --> 00:03:21,623 which then sends back a response with the website code. 74 00:03:22,530 --> 00:03:24,090 Now, what actually happens 75 00:03:24,090 --> 00:03:26,370 is a slightly different thing though. 76 00:03:26,370 --> 00:03:28,220 This request is sent, 77 00:03:28,220 --> 00:03:32,460 but it's actually not sent with just this domain. 78 00:03:32,460 --> 00:03:36,500 Instead, all the devices that take part in the Internet, 79 00:03:36,500 --> 00:03:41,040 so to say, have so-called IP Addresses. 80 00:03:41,040 --> 00:03:43,370 IP stands for Internet Protocol, 81 00:03:43,370 --> 00:03:46,960 and it's another standard that controls how devices 82 00:03:46,960 --> 00:03:49,183 in the internet are identified. 83 00:03:50,090 --> 00:03:53,540 Now, IP addresses look something like this and therefore, 84 00:03:53,540 --> 00:03:56,670 of course, they are pretty hard to memorize for humans, 85 00:03:56,670 --> 00:03:58,680 but every device in the internet, 86 00:03:58,680 --> 00:04:02,500 including your computer, has such IP address. 87 00:04:02,500 --> 00:04:05,740 And these IP addresses are actually needed 88 00:04:05,740 --> 00:04:09,500 for establishing connections and talking to each other. 89 00:04:09,500 --> 00:04:11,350 Now, since they are hard to memorize, 90 00:04:11,350 --> 00:04:12,740 we have these domains, though, 91 00:04:12,740 --> 00:04:15,100 which are easier to memorize for humans, 92 00:04:15,100 --> 00:04:17,680 but which are not used by default 93 00:04:17,680 --> 00:04:21,240 to establishing these connections and sending requests. 94 00:04:21,240 --> 00:04:22,950 And the reason for this is that, 95 00:04:22,950 --> 00:04:25,960 all devices that are part of the internet need 96 00:04:25,960 --> 00:04:28,340 such a unique identifier. But of course, 97 00:04:28,340 --> 00:04:32,080 for example, your computer, if it's not hosting a website, 98 00:04:32,080 --> 00:04:33,690 which it typically isn't, 99 00:04:33,690 --> 00:04:36,050 doesn't have a human readable domain. 100 00:04:36,050 --> 00:04:38,040 That's why we don't use domains 101 00:04:38,040 --> 00:04:39,900 for establishing connections, 102 00:04:39,900 --> 00:04:42,480 because every device has a IP address 103 00:04:42,480 --> 00:04:45,740 but not every device has a domain. 104 00:04:45,740 --> 00:04:48,690 However, as a user, as a visitor of a website, 105 00:04:48,690 --> 00:04:50,820 we, of course, want to enter such a domain 106 00:04:50,820 --> 00:04:53,540 to view the website, not the IP address. 107 00:04:53,540 --> 00:04:57,270 Though, if you knew the IP address of a specific website, 108 00:04:57,270 --> 00:04:58,940 you could enter this, as well. 109 00:04:58,940 --> 00:05:02,020 But of course, typically, we don't know that. 110 00:05:02,020 --> 00:05:04,210 That's why, as part of the Internet, 111 00:05:04,210 --> 00:05:07,500 we have some special servers which are operated 112 00:05:07,500 --> 00:05:12,500 by global organizations, the so-called DNS servers. 113 00:05:12,830 --> 00:05:15,680 DNS stands for Domain Name System, 114 00:05:15,680 --> 00:05:19,940 and these are servers that contain mapping tables, 115 00:05:19,940 --> 00:05:24,510 you could say, long tables with all the known domains 116 00:05:24,510 --> 00:05:28,160 and the IP addresses that belong to these domains, 117 00:05:28,160 --> 00:05:31,260 so, the IP addresses off the remote computers 118 00:05:31,260 --> 00:05:35,320 that host the websites that belong to certain domains. 119 00:05:35,320 --> 00:05:38,060 And when you enter a address like amazon.com 120 00:05:38,060 --> 00:05:41,220 in the browser, or academind.com or anything else, 121 00:05:41,220 --> 00:05:46,080 your browser actually first talks to such a DNS server 122 00:05:46,080 --> 00:05:49,250 to translate the domain into an IP address. 123 00:05:49,250 --> 00:05:51,900 And then, once that IP address was returned, 124 00:05:51,900 --> 00:05:55,770 then your browser sends the actual request 125 00:05:55,770 --> 00:06:00,040 to this remote machine, to this server serving a website, 126 00:06:00,040 --> 00:06:03,570 which is now identified with help of that IP address. 127 00:06:03,570 --> 00:06:05,800 That's what actually happens here. 128 00:06:05,800 --> 00:06:09,370 And even though that might sound like a long taking process, 129 00:06:09,370 --> 00:06:12,620 this is actually all super quick and only takes a couple 130 00:06:12,620 --> 00:06:15,010 of milliseconds, but that's what's going on 131 00:06:15,010 --> 00:06:16,090 behind the scenes. 132 00:06:16,090 --> 00:06:18,530 And that's all of the reason why, 133 00:06:18,530 --> 00:06:20,770 when you want to publish a website, 134 00:06:20,770 --> 00:06:24,520 you typically have to buy such a domain first, 135 00:06:24,520 --> 00:06:27,240 at least, if you want to have a custom domain. 136 00:06:27,240 --> 00:06:30,770 Because these domains have to be registered globally, 137 00:06:30,770 --> 00:06:33,980 you can't just come up with one because, of course, 138 00:06:33,980 --> 00:06:37,240 they must only be used once, they have to be unique, 139 00:06:37,240 --> 00:06:40,570 and therefore, you wouldn't be able to, for example, 140 00:06:40,570 --> 00:06:43,770 register amazon.com if you wanted to do that, 141 00:06:43,770 --> 00:06:47,770 because that domain is already taken by the Amazon company. 142 00:06:47,770 --> 00:06:51,140 But you can take other domains. And once you bought them, 143 00:06:51,140 --> 00:06:53,940 they are registered and they are added 144 00:06:53,940 --> 00:06:57,070 to these mapping tables, so to say. 145 00:06:57,070 --> 00:06:59,710 And that's all that's important to understand 146 00:06:59,710 --> 00:07:02,750 and to be aware of. We have these IP addresses, 147 00:07:02,750 --> 00:07:04,180 which are actually used, 148 00:07:04,180 --> 00:07:07,560 and domains, which are translated to these IP addresses. 149 00:07:07,560 --> 00:07:09,580 Now as a last note, I did, 150 00:07:09,580 --> 00:07:11,620 of course, say that every device 151 00:07:11,620 --> 00:07:14,390 in the internet has such IP address, 152 00:07:14,390 --> 00:07:16,910 but you don't need to worry that this means 153 00:07:16,910 --> 00:07:20,810 that other people could start connecting to your computer. 154 00:07:20,810 --> 00:07:23,010 This, by default, is not possible 155 00:07:23,010 --> 00:07:25,860 because you can still control whether a device 156 00:07:25,860 --> 00:07:28,310 is allowing incoming traffic or not. 157 00:07:28,310 --> 00:07:29,310 And by default, 158 00:07:29,310 --> 00:07:32,900 your computer does not allow incoming traffic. 159 00:07:32,900 --> 00:07:35,920 These servers, which are serving websites, 160 00:07:35,920 --> 00:07:38,910 are configured to allow incoming traffic. 161 00:07:38,910 --> 00:07:41,180 Your computer typically is not, 162 00:07:41,180 --> 00:07:44,100 so it has this IP, but it still isn't reachable 163 00:07:44,100 --> 00:07:46,820 by everyone in the worldwide web. 164 00:07:46,820 --> 00:07:50,740 And with that, we now had enough theory for the moment. 165 00:07:50,740 --> 00:07:52,030 That's it, for the moment. 166 00:07:52,030 --> 00:07:55,360 Let's now see how you can get the most out of this course 167 00:07:55,360 --> 00:07:57,620 and how you can take this course before we, 168 00:07:57,620 --> 00:08:01,500 then thereafter, dive into the actual code you can write, 169 00:08:01,500 --> 00:08:04,970 and learn more about web development step-by-step, 170 00:08:04,970 --> 00:08:06,143 from the ground up.