The free money bonus is a bonus you get when you sign up with an online casino. It's something you can choose to claim or not claim when your are doing the registration. The free money you get are always limited with terms and conditions.
These are most often wagering requirements mening that you need to wager your bonus amount a specific amount of times before a withdrawal. The wagering requirement can be hard to meet but the free money bonus is still a great way to try out a new casino or a specific game .