What does it mean to play games, to be a player? You'll never get the same answer twice and most of them are right in one respect or another. Playing games is fun, its fancy free and we've all done it since we were kids; but role playing games are games we know all too well whether we realize it or not. You've played role playing games since you were too short to get your own stuff out of the cupboard. When you played cops and robbers, pretended to be a knight slaying a dragon, played house and a bunch of different other games you were role playing. The only difference now is that you use rule books and the fantasy is much more detailed.
This doesn't really tell you what being a player means, but it's a start and if you don't know by the end of this guide, then you'll just have to play and find out for yourself.