Free play refers to a specific type of promotion that is offered by some casinos, in which players are given a certain amount of money to use on certain games, usually slot machines. This money is not real money, but rather a form of "play money" that can be used to play the games but cannot be cashed out or withdrawn.
Well to start off, FreePlay is basically defined as credit to play in a slot machine for free in order to win real money. Anything you make off of the FreePlay, is yours to keep...or play with.