Forty Thieves is a classic card game that is played with a standard deck of 52 cards. The objective is to build eight foundation piles, one for each suit, in ascending order from Ace to King. Players can move cards between tableau piles and the foundation, following specific rules about card placement. The game is typically played by one person, making it a popular solitaire variant. Players start with a tableau of 40 cards, arranged in a specific layout, while the remaining cards form a stockpile. Strategic thinking and planning are essential for successfully completing the game.