In short a bowling set is bowling 3 games, after that you see how many pins you knockdown total. In bowling leagues they use this 3 game set to see who wins and some peolpe play this 3 set bowling set to to see who is the best. The bowling set gives you a chance to come back when you lost one game to get back in the game.
To find out your bowling average just bowling 3 games then add all three scores then divide that number by 3 and the will tell you your bowling average. So thats what a bowling set is.