The wagering requirement or as often referred to as "rollover or playthrough" is a multiplier that represents the number of times you have to play through a bonus before you are able to withdraw any winnings.
A wager refers to the amount of money you stake, bet with each spin of reels or hand of cards.
A standard 1x (one-time) wagering requirement applies to deposits before they become cashable while playing slot games.
A standard 10x (ten times) wagering requirement applies to deposits before they become cashable while playing table games and any other games.
The wagering requirement for bonuses varies for each promotion. You are able to check the wagering requirement, along with the amount and the percentage you have wagered for your active bonus on your bonus page.