Question regarding internet connectivity

[thegreekboy]

I am planning on building myself a computer. I have all parts budgeted out and picked, and just need to raise the money to buy the parts. Lately I've been dissecting my plan and seeing if there are any holes that might cause trouble.

I've recently found one of said holes. I have no idea how to hook a computer up to the internet. Can someone explain how to do this to me? Do you hook a cable up to your phone line, have your ISP do it, or what?