Gamemaster's screen

The gamemaster's screen separates the players' view of the game (top) from the gamemaster's private information and dice rolls (bottom)

A gamemaster's screen, also called a GM's screen, is a gaming accessory, usually made out of either cardboard or card stock, and is used by the gamemaster to hide all the relevant data related to a tabletop role-playing game session from the players in order to not spoil the plot of the story. It also hides any dice rolls made by the gamemaster that players should not see. In addition, screens often have essential tables and information printed on the inside for the gamemaster to easily reference during play.