beginner needs help!!

I have a Compaq 5220. I am trying to download a driver. (?) I don't even know what a driver is! I just bought a new music CD that is also supposed to play on the computer (CDExtra). Nothing came up when I put the CD in, so I went to the www.cdextra.com site which led me here saying I needed to download a driver. What are drivers and how do you know which one you need?? HELP please! Any comments, advice, suggestions, anything would be helpful! Thanks!