If you're a 10 handicap golfer what does that mean and how is your handicap calculated?

A ten is pretty good. What you do to calculate handicaps is take your last twenty rounds, then throw out your highest ten scores (these are not a factor) then average your ten best scores and that will be your handicap, and it will not be a whole Number, it will be like a 10.1 or a 11.7, which will be averaged by the slope of the course you play, which means difficulty and that will vary a little on other courses you play if they are harder or easier. Good luck.