As a player in the game you are creating a fiction with other players in the game. The fiction is the imaginary story that you collaborate on which informs later choices you make. It has intuitive rules that often follow real life or if they diverge, they do so in ways that you and your fellow players have decided on together.
There are two kinds of player in the game - those that have authority over one character and everything pertaining to that character and actively roleplay what that character does, and one player who has authority over everything else and is the main prompt to the other players to have them react to the universe in general. This player is often referred to in other roleplaying games as the Game Master or Dungeon Master. The player in charge of everything other than the protagonists in this game is called the Grandfather (after the Grandfather Paradox).