Initiative
Decides the order in which characters and creatures take their turns during combat.
When a fight starts, everyone rolls initiative. Highest goes first, then the next highest, and so on. That list is the turn order, shown beside the map during combat. Nobody can move or act until everyone has rolled.
In Fantasy RPG
Fantasy RPG: d20 + the Dexterity modifier. Players roll their own; the app rolls for the GM's creatures.