Someone explain URLs? [rep awarded]

[Dracula]

I am just curious about how on photo upload sites, when you view the direct link to your image, the first part (before the .photobucket.com or .tinypic.com) is a i## rather than www. Is it connected at all to your IP address?
For example:

(you need an account to see links).....

(you need an account to see links)......

Can someone explain what this means in simple terms? Thanks!