In their most simple form, a tabletop roleplaying game (TTRPG) is a form of storytelling where an individual or group participates in a story that is in some way reactive to decisions that they make.
Perhaps one of the simplest versions that many of us have played are “pick a path” style stories, where at certain points we are given options to choice, or “pick”. These choices then lead to a different “path” for the story to take.
The appeal is obvious: YOU are effectively choosing how the story ends, not the author (although in the case of pick a path books, the number of potential endings is necessarily finite).