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is not real money, but rather a form of "play money" that can be used to play the games but cannot be cashed out or withdrawn.

First of all, you won't be able to withdraw any winnings that you make with your free play balance. This is because the free play balance isn't real money, it's just a way for the bookies to get you started.