The promotion of free play slots is one that casinos have been given for several years now. When we talk about free play that means when you claim one of these bonuses you are not actually playing in the main casino but instead you are playing in a free version of the casino so all the wagering does not count for coin in and out within the casino real play games.
So basically you are winning fun money but that money can be transferred into real money in the main casino. This only happens if you have wagered it enough in the time allowed to earn money off the bonus. Most will put a restriction on how much can be transferred so it wont be like you can move a lot of money just a bit. Players do seem to like this type of promotion and often search for the free play slots offers, however the casinos are starting to remove this offer from their sites and moving on to different promotions. For now there is some that still exist and if you haven’t tried them yet you should as it may be a thing of the past shortly.