Carfax question?

Has anyone used carfax before? Let me know what it tells you, how dependable it is. And if at all possible, does anyone have an account with them? I know that some if you pay 25 bucks, you get an unlimited/lifetime/yearly, or something number of checks you can do. If someone does, can they look into a vin # for me? I would like to save 25 bucks if possible...thanks a ton...