A Free Bet is a bonus for sports betting, where you can place a free bet, a bet without using your own money, and any winnings are usually credited as withdrawable cash.
On the other hand, a Free Spin is a casino bonus offered for slot games that lets you spin the reels without using your own money. Any winnings from these spins are typically available for withdrawal as cash.
The winnings received do not include the amount that was bet.