The wagering requirement (also known as playthrough or rollover) is the most critical part of any bonus offer. Mechanically, it is a multiplier that represents how many times you must bet the bonus funds before they convert into withdrawable cash.
Why does this exist? It prevents players from claiming a bonus and immediately withdrawing it, which ensures the bonus is used for its intended purpose: gameplay. You will encounter two main types: Bonus-Only wagering, where only the bonus amount is multiplied, and Deposit+Bonus wagering, where both your deposit and the bonus are multiplied. The latter results in a higher total amount to bet before withdrawal.
Progress is tracked automatically by the system. Every bet you place reduces the remaining wagering amount. You can find the specific multiplier for any offer in the Promotions section or the associated Terms and Conditions link.