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

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

RTP is a game’s long-run average return: 96% RTP means a 4% house edge. Volatility describes how uneven wins and losses may be. In a short session, results can differ sharply from the average—there’s no guaranteed return.