How do you work wi-fi?

I know there's a lot of hot spots in town but would I need any new equipment to use them? I have a very new computer with Windows 7 and would like to be able to surf the net without being limited to the hourly time limit. I've got a dongle, could I use that without any credit on it? Also, while I'm on the subject, can you explain how Bluetooth works and what it does please? Everybody who gives a constructive reply receives a thousand blessings!