Risk is a strategy board game of diplomacy, conflict, and conquest for two to six players. The standard version is played on a board depicting a political map of the world, divided into 42 territories, which are grouped into six continents. Turns rotate among players who control armies of playing pieces with which they attempt to capture territories from other players, with results determined by dice rolls. Players may form and dissolve alliances during the course of the game. The goal of the game is to occupy every territory on the board and, in doing so, eliminate the other players. The game can be lengthy, requiring several hours to multiple days to finish. European versions are structured so that each player has a limited "secret mission" objective that shortens the game.

Source: Wikipedia