When you pick an online game, the RTP tells you how much you can expect back...

https://fantasynamezone.com/why-players-are-paying-more-attention-to-how-online-games-actually-work/

When you pick an online game, the RTP tells you how much you can expect back over time—think of it as the house's average payout rate. Volatility shows if wins come quick and small or rare and big