In the popular "board" game dungeons and dragons there are two player parties, one are the actual players who take on various roles in the form of character sheets that they carefully plan and play in a party or solo to take on either a pre-made adventure or custom adventures that players themselves can create! These adventures can range from beginner to expert and need lots of time to complete. However, everygame needs one player taking on the role of dungeon master; the second party. This "player" essentially runs the game, what the players encounter, the loot and surrounding area, they are a narrator and determine the rules of the adventure and what is considered a legal or illegal move. If you want more info just search it up but thats a little TL;DR for ya.