Playthrough is the total sum of bets that need to be placed before your winnings can be withdrawn. The total amount of bets you make, (win or lose) must add up to the playthrough before you're able to convert winnings into money that can be withdrawn. Each time you spin/ place a bet, the playthrough amount will decrease and you'll be one step closer to being able to withdraw your winnings. Once the playthrough amount is 0 the account balance will become available for withdrawal.