A cashable casino bonus is one that can be turned into real money by fulfilling a wagering requirement. Up until that has happened it can only be used for wagers.
One important detail in the T&C of Cashable Bonuses is if only wagers made with bonus money counts toward the wagering requirement, or if wagers made with ‘real money’ counts as well. The latter being more advantageous for players.
A withdrawal request before the wagering requirement has been met will in most cases forfeit any bonus amount on the player’s account.