How does a Netbook connect to the internet?

I have only had a desktop, never even a laptop, so I am clueless as to how you get connected to the internet via a netbook. Do you pay a monthly fee like I do for internet use on my desktop? How does it work when I'm not home, like traveling in a car? I use the computer mostly for pleasure, not for business, and obviously I'm pretty computer illiterate. Any help would be appreciated.