When you receive a bonus (either free play or in cash form), you will be required to place a certain amount of wagers before a payout can be requested.
For example, if you get a 10% cash bonus on your deposit and the bonus has a 3 times rollover, this means you need to wager both the deposit amount and bonus amount over 3 times before requesting a payout. In other words, you need to wager $330 ($100 deposit + $10 cash bonus =$110 x 3 = $330 in wagers).