A wagering requirement (also known as "playthrough" or "rollover") is a multiplier that determines how much you must bet before bonus funds are converted into withdrawable cash. This mechanism exists because bonuses are promotional tools; without wagering, players could claim a bonus and immediately withdraw it without actually playing any games.
There are two primary types of wagering structures: Bonus-Only, where you only need to wager the bonus amount itself, and Deposit + Bonus, where the multiplier applies to both your initial deposit and the bonus credited. The latter requires a significantly higher volume of betting to clear.
Tracking your progress is simple: as you place bets, the "remaining wagering" amount decreases. Note that the multiplier is not a fixed number across the site; each individual offer has its own specific requirement. You can find the exact multiplier for any given promotion listed clearly alongside the offer in your account dashboard.