Free spins are the spins on the slot machines which a casino gives you for free. The chance of winning the jackpot is not that big, and that is why a casino gives you this opportunity. The chances are low, but players still win money on slots.
When using free spins, money is not debited from the principal balance. All winnings are credited to the bonus account. After the wagering requirements are met, the money can be sent for withdrawal. Free spins, like other casino bonuses, are subject to certain conditions.