A roleplay module is a publication designed to be used as part of an RPG (role-playing game).
History and specifics
This could include various types of reference books and short stories designed to guide players through a game. These publications have separate sections for players and the person running the game, as certain details could be considered spoilers that could ruin the game if they are perceived by the player. As such, many modules come in sets so the player does not accidentally access information they should not be privy to. If a module consists of a single book, there will sometimes be instructions included for certain sections to be photocopied and given to the player.