How the Web works

First, the "Internet"

The Internet is a global network of computers connected together with the ability to communicate with each other. If your computer is online—which apparently it is, since you are reading this article—it's connected to the Internet.

The WWW

The World Wide Web is a large network of hyperlinked files that are accessible somewhere on the Internet. (Hyperlinks:  the links on a Web page that take you to another page, website, or open a PDF or video.)

The Web is not the Internet

The Internet and the World Wide Web are not the same thing. Actually the Web is a subset of the Internet. 

The Web uses the Internet, to pass particular types of information designed to graphically display text, images, movies, and audio on local computers. 

Think of it this way: the Internet is like a telephone line carrying the signals back and forth, and the Web is like the telephones on either end that know how to use those signals intelligently.

(As a matter of trivia, they are both capitalized).

A little history

The Internet has been around in various forms since the 1960s, first connecting research and military facilities and major universities with a patchwork of methods. Things were standardized in the early 80's and the Internet took off. Those of you old enough, may remember being able to send email and view plain text and some images, but without any graphical interface—black Courier fonts on boring white backgrounds.

The Web has only been around since 1991 when Sir Timothy Berners-Lee, then a researcher at the accelerator lab at CERN Switzerland, invented it to take advantage of the Internet as a conduit for scientists to share information and research using hypertext documents (documents containing hyperlinks mentioned above) and images. To make it work he had to develop the methods to transfer the information intelligently to and from specific locations (Web sites) and then a browser to make it all look pretty.

The beautiful thing—he didn't hog it for himself to become a gagillionaire. Instead he magnanimously made it free for everyone.

And no, Al Gore didn't invent the Internet or the Web.

Web Sites

Web sites are a collection of related files grouped on a special uniquely identified computer or Web server somewhere on the Internet. Some of the files contain special coding (you might have heard about HTML) that create the hyperlinks and organize the content and look of the site usually in the form of text, typefaces, images, video, audio, etc.

Web Servers

A Web site's files reside on Web servers—special computers connected to the Internet. What makes these special? Well, a server is smart enough to know where all the Web site files are located on its hard drive and then how to "serve" them up, or make them available to those looking for them. Just like your own computer can find that Word file or picture.

They can also provide security through SSL certificates (the little padlock you see when you are checking out of an online store), encryption, authentication, and credit card verification for e-commerce.

Web Hosts

Web hosts are usually commercial entities that sell and maintain Web servers. They usually provide a way for their customers to update their Web sites through special access, e.g., FTPs, which allow users to view and update the directory tree of Web files through text editors and uploads. They can also provide email services, file storage, and often, domain name registration (usually as agents for larger DNRs like GoDaddy...more below).

So, in summary, Web sites are a group of related files that reside in a designated place on a Web server that are accessible via the Internet through Web browsers. It all boils down to files, on computers, connected together, that we can have access to.

Domain Names

We find lots of things in our lives by using some unique number or code, e.g., Dewey decimals to find a book in your local library, or a phone book to find the phone number of a friend. Finding a Web site is not much different.

Back to our telephone analogy. Let's say you have your grandmother's number recorded in your smart phone's address book. You know which number it is because you probably have it recorded under some recognizable name like "Grandma." It's much easier to remember her name than her number. So, when you want to call Grandma, you tap her name and your phone looks up her number, dials it, and sends out your request to talk to her in the form of a ring.

Domain names serve a similar purpose. All computers, even the one in front of you, have unique addresses called IP (Internet Protocol) addresses. They usually look something like this: 17.172.224.47 (apple.com). If you wanted to visit the Apple site, remembering their IP address is harder than simply remembering their domain name. So, the domain name acts as an alias, or short cut, for a site's IP address—you use an easy-to-remember name instead of a bunch of numbers.

URLs

URL's  are misunderstood and might be a bit geeky for this article. But quickly: A URL is actually just part of a larger entity, the "URI." So,  a URI = URL + URN. Example: URL = "http://" + URN = "apple.com" A URI can also include other more specific address for a page or file: http://support.apple.com/kb/HT2109. In summary, URI is more accurate than URL when referring to a Web address. But best not to correct your friends. 

Where do domain names come from?

Domain Name Registrars (DNRs), also called domain name hosts, are organizations officially sanctioned to distribute or sell domain names. Some DNRs are household names, like GoDaddy or Network Solutions.

Besides selling domain names, they:

1. They maintain a list of domains they "host" on "authoritative" name servers and where their locations, or IP addresses, can be found on the Internet.
2. They are responsible for sending that address information back to browsers so you can find what you are looking for. More on this in a minute.

Secure Certificates

SSL certificates, issued by Certificate Authorities (e.g., Verisign, Comodo, GoDaddy, Thawte) can be applied for, approved, and installed on a site's Web server to authenticate the identity of the site for encrypted communications, as needed in e-commerce transactions when credit cards are being sent across the Internet. The authentication process is trigged by a URL with the https:// prefix. A properly secured site will usually show a closed padlock icon in the browser. Never submit your credit card unless you see the lock!

Web browsers

You really can't view anything on the Web without a Web browser. A browser (Firefox, Safari, Internet Explorer, Chrome) is a program, or software, on your computer or smart device that does the heavy lifting of finding and displaying Web sites on your screen. Browsers look up the location of the Web site you want and then make the connection, pulling down the necessary files from the Web host.

So, how does a browser find a Web site?

We finally get to put together all the pieces and see how they work. See accompanying diagram.
Example: you are sitting at your computer and want to visit the online Apple store. So...

1. You enter "apple.com" into your browser's address field (most modern browsers assume th full URI, i.e., "http://www.")
2. Your browser, connected to the Internet by your Internet Service Provider (or ISP, e.g., Comcast, AT&T), sends a request to your ISP that maintains its own mini Domain Name Server (DNS) with a list of sites on its own network.
   a) If the domain is found in it's own DNS, it sends the IP address of the site back to your browser (jump to #5).
   b) If it doesn't find it there... 
3. The DNS forwards you on to the next larger DNS up the chain, and so on, until it finds it and...
4. Sends back the IP address for the site. Note: a single DNS doesn't store all the domain names on the Web, they are spread out among all the DNSs. This is why some Web sites appear to take longer to load in your browser—it may have to check several DNSs to find the domain you are looking for.
5. Once your browser receives the correct IP address of the Web host or Web server where the Web site files reside, it retrieves the files by sending out a specially coded request to the host that then...
6. Sends back the files for the desired page of the site. The browser reads through and interprets all the files, then builds and displays the Web page with any text, graphics, colors, fonts, pictures, and videos linked to it.
   Optional (5a): if you are trying to connect to a secure site (you'll see https:// in the address field of your browser), e.g., if making a credit card payment, your browser will "ask" the Web server to "authenticate" the site as possessing a valid SSL certificate. Check to make sure the padlock icon you see in the browser is "locked." Secondarily, if you submit a credit card, the Web server will use the site's payment gateway to verify the card number with the site's merchant account or bank.

Again, see the attached diagram.