RTP is a game’s long-run return: 96% RTP means a 4% house edge on average....

https://www.quantifiedstrategies.com/rtp-variance-and-expected-value-applying-a-quantitative-framework-to-online-casino-gaming/

RTP is a game’s long-run return: 96% RTP means a 4% house edge on average. Volatility describes how uneven wins can be. Short sessions can differ sharply from RTP, so your balance may drop quickly or rise unexpectedly.