Volatility (sometimes called variance) describes how wins are distributed over time, independent of RTP.
Low-volatility games pay out more often but in smaller amounts, which suits players who want their bankroll to last longer per session. High-volatility games pay out less often but can produce much larger individual wins, usually concentrated in a bonus round.
Neither is objectively better — it depends on what you're optimizing for. A player with a fixed, small budget who wants to play for an hour is usually better served by a low or medium volatility game; a player chasing a single large multiplier hit will gravitate toward high or very high volatility titles.
