RTP is a long-run average; house edge is the casino’s expected share of wagers:...

https://johnnywrbo401.wpsuo.com/why-do-high-variance-games-have-long-dead-spells

RTP is a long-run average; house edge is the casino’s expected share of wagers: 96% RTP means a 4% house edge. Volatility measures how uneven results can be. Over a short session, wins or losses may differ sharply from the average.