A round is the segment of gameplay in which every character can do as many actions as they are allowed to before all of their actions are refreshed. Different role-playing game systems may use rounds for all aspects of gameplay, for some parts of gameplay only (e.g. pressured situations like combat), or not at all.
In RPGs with initiative systems, a round may be the total of every character's turn from first to last (in turn-based initiative systems), or the period of time in which every character spends shots until no more shots can be spent (in shot-based initiative systems).