Sometimes an online casino will grant an incoming patron a certain amount of "free play" in order to sample some of the casino's games, with the opportunity to win money that can be applied toward a playing account. This has proven to be an extremely popular promotion to do with players.
If an online casino can draw in and sign up players by offering them some free credits, you know that they are going to try to get the most out of that policy. And that is what often happens in the hyper-competitive world of online gaming. For the player, there is an interesting opportunity to take a shot at the casino with no risk. So with the downside low, there is a chance that the player will actually like what the casino has to offer and possibly become a real money customer.
Of course, that is the ideal anyway. An online casino is not in business to give customers free shots at its games, including the slots, and allow them to walk away with the money they have made. That would be a fantasy, and wouldn't it be nice if the world worked out that way for everybody? Sure it would. But the way the concept of these free credits works, there is a "what can you lose" attitude that is hard to resist.
A prospect may come in and get $100 in free play from an online casino, with the idea that there might be a certain amount of time to play the games (the type of games may be restricted) and then at the conclusion of that period the amount of money that is won by that person can be converted into an account that is subsequently opened, and even then it may be subject to certain wagering requirements. But what this "free play" situation does is allow the prospective customer an opportunity to experience what the casino is like. They will download the software and be able to evaluate the convenience level, the quality and variety of the games and the overall quality of the software suite itself, and make a more intelligent decision as to whether he or she wants to make a real money deposit.
Whether it is free play on a wide variety of the casino's games, or free spins on one of the slot games, the money that could be won during the specified period of time (of which there is a limit) can only be applied as a percentage of funds that are eventually deposited into the online casino to open up an account. So there is no free lunch, as they say.