They should know, though, that very few athletes ever make it that far. It's a good idea, then, to have another job in mind as well.
Professional athletes play sports in front of an audience and get paid for it.
Fans enjoy seeing these athletes play so much that they are willing to pay to watch a game or match. Professional athletes are performers or entertainers, a lot like actors and musicians. They must perform well in each game or risk losing each game. If they don't play well, they won't last long in this job. They must be in the best possible shape.