Free spins is the most common slot bonus round: a set number of spins that cost nothing extra, played at the stake you had when the feature triggered. It is usually started by landing three or more scatters.
What makes a free spins round worth more than ordinary spins is what the game adds. Typical enhancements include a multiplier on wins, sticky wilds, extra wilds on the reels, removal of low symbols, or a different set of reel strips. Many rounds can be retriggered to add more spins.
The round is not a gift: its expected value is part of the game's published RTP, paid for by the base game.
Do not confuse this in-game feature with a casino's free spins offer, which is a promotion with its own terms. See our free spins feature page.