What exactly is happening when we're browsing the web?

Let's take a look at some of the most basic tasks while surfing the web. First, I'm going to load Firefox. Firefox is like Internet Explorer's cool uncle that has all of the nice toys. 

Immediately Firefox took me to my "Home Page"... but looking in the address bar it says file:///usr/share/ubuntu-artwork/home/index.html 

Let's break down the elements of a URL.

Protocol/Scheme:

	- http
	- https 
	- file
	- mailto
	- ftp

Host:
	- www.example.com

Port:
	- :80

Path:
	- /share/ubuntu-artwork/home/

Query:  
	- month=july

Fragment:
	
	- #week3 

Immediately, the browser dissects these segments and fetched the appropriate files. Since the file protocol was used, the browser does not go out to the internet. 

The browser then goes to the specified location/path and fetches the file requested. In this case, it is index.html. The browser then passes the file to what is called a rendering engine. Rendering engines are the part of a web browser that 'paints' the web page onto your screen. 

Let's go to another website. Google. If you just type www.google.com, your browser is smart enough to know that you really mean http://www.google.com. Fetching a website from an external server is a bit more complicated, and warrants an explanation. Networked computers talk to each other over something called TCP/IP. In order for TCP/IP to communicate to another computer, it needs a host. Hosts are identified by a string of numbers called an IP address. Think of this like your postal address. 

IP Addresses are divided into 4 triples [0-255].[0-255].[0-255].[0-255]. With computer systems moving and rebooting, a need was created to uniquely identify a system with a non-changing address. Enter something called DNS. DNS (Domain name System) is what translates www.google.com into an IP address that can be spoken to over TCP/IP.

Now that we have Internet 101 out of the way, how does this relate to Firefox loading Google? Firefox uses your operating system's DNS capabilities to look up the IP address associated with Google.com. After that, it uses TCP/IP to talk to that IP address and make a request to Google for Google's homepage. Desperate for your traffic, Google's server agrees, and sends your computer the code that your browser passes to its rendering engine, and then paints on your screen. 

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