To sum it up, these are slot games that you don’t have to pay to play. You will find 3 main types around online casinos:
Try For Free Slots - or free play slots; these are games that casinos will let you play for free. You can’t win real cash playing a free slot like this - but it’s great for practice.
No Deposit Free Spins - on occasion, a casino will offer free spins on a particular slot or set of slots, usually as part of a welcome offer. When you play your spins, you will win a bonus. In most cases, this bonus is yours to keep and withdraw if you can meet the wagering requirements.
No Deposit Slots Bonus - if you want a bit more freedom and don’t want to be restricted to just one game, then you may prefer a broader bonus. Like free spins, if you can meet the wagering - then this will become real cash that can actually become withdrawable.