Sports Interaction applies rollover and betting requirements in the interests of fair gaming, so that players will play in the Casino, Sportsbook or Poker before attempting to cash out or withdraw. In the Sportsbook, only bets with prices of 1.51 or higher count towards rollover count.
In simple terms, this means that when you receive a bonus, you must bet (or rollover) the bonus cash and deposit that you receive a set number of times, before you can turn it into real cash and withdraw it.
Promotional offers range in betting requirement type; for example Bet Credits require you to bet your own real money before releasing the Bet Credits which have no rollover.