an0n's guide to IP's and domains[/u][/i]
Every computer across the world is identified by way of an IP block. There is a regulatory body (I forget who it is) which dishes out IP blocks to whoever can afford them.
So some hosting place may buy the entire IP block for 215.89. Then whenever someone tries to access a computer with an IP starting with 215.89, they will be directed to whoever bought the domain block where they will be presented with some form of nameserver (I forget the proper name for the IP ones so I'll refer to them as nameservers) and the following happens:
215.89: Hello, I serve everything under 215.89. What IP do you want?
YourComp: I want 215.89.123.46
215.89: Ah, okay, I know where that is. Gimme a minute. *sends you to 215.89.123 nameserver*
215.89.123:[/u] So you want 215.89.123.46, eh? Just a second..... *sends you to a specific computer*
215.89.123.46: 403, Forbidden. *closes connection*
So you get the registered server for the first block of numbers, which sends you to the server for the second, which sends you to the third and finally the the fourth which is usually a standard computer. So as you add numbers to the end, you narrow down the number of computers until you end up with a single one. However, domains work the other way round.
I think it's Verisign that owns all the top level domain (.com, .net, .org) and say you wanted ftp.3dap.com, the following would happen:
.com: What do you want?
YourComp:[/u] I want ftp.3dap.com. Know where I can find it?
.com: 3dap, eh? Sure. Gimme a second. *directs you to the registered nameserver for 3dap.com*
3dap.com: You're the guys wanting ftp.3dap.com, right? *sends you to the appropriate computer for ftp.3dap.com*
Now, if ftp.3dap.com was running a nameserver, then you could have money.ftp.3dap.com. So every time you wanted to create a tree of addresses under you, you would add them to the beginning of the name.