How do you get wireless internet connection on the Dell Inspiron mini netbook?

The network that I’m already signed up with is At&T and they provide internet access for my desktop. However, it is not wireless. Right now, I have no wireless connection if I were to just use my netbook. In addition, what is a router and a modem? Please help!

If you are with at&t they can provide a wireless router and setup as part of the monthly billing