As the name suggests, this type of bonus allows you to place free bets equal to the value of bonus. For instance, if you got bonus worth $100 at the time of sign up, you can place bets worth this amount in various games. This is really good option for trying new games on various casinos. You might get lucky and make some money without the need to invest anything.
Did any of you made huge money with this bonus amount ?
Nope, never work on me. The roll over to withdrawal the bonus is too much like 40-50x roll over, sometimes even more and i always failed. My experience with free cash bonus always ended with lose all my balance. So i never claim any free cash bonus again.