This guide explains how paylines differ from cluster wins, which symbols wilds...

https://wiki-burner.win/index.php/What_Are_Persistent_Symbols,_and_Do_They_Carry_Over%3F

This guide explains how paylines differ from cluster wins, which symbols wilds can replace, and how scatters start bonus rounds. It also shows why a filling meter can track progress without promising a win is coming.