Federal Stafford Loan Unsubsidized?

Ok, I didn't qualify for a subsidized loan but I did for an unsubsidized. I am not sure how it really works, I'm lost. Can someone explain to me in plain English, how it works. Also what is the beginning interest rate, and I heard that it accrues while your in school....what does that mean??? So if I pay it off earlier would that be better?? I'm confused. =/ help?