The Monty Hall problem is a well-known probability puzzle centered around three doors, two with a bad prize hidden behind, and one with a good one.

The Monty Hall problem is a probability puzzle, loosely based on the American television game show "Let's Make a Deal" and named after its host Monty Hall.

In the problem the player of the game show is asked to pick one of 3 doors to open and hopefully get the best prize, a car (and not a goat). The host, Monty Hall, then opens a different door revealing one of the two dud prizes, a goat. The host then asks if you'd like to stick with your initial choice or change doors. The probability problem comes into play when deciding whether or not it is better to change doors.

Questions with this tag often concern more complex or interesting variations of the original Monty Hall problem, although the original itself has also been posted here.

For more information the Wikipedia article on the Monty Hall problem can be found here.