It’s a great problem. The Monty Hall Show was a 1950s US TV quiz. At the end of the quiz the winner had an opportunity to win a car. The car was hidden between one of three doors and the winner tried to guess which one. There were buckets of water behind the others.
But there was a twist. After the winner had picked a door, Monty would open a different door and show him or her a bucket of water. Show the car had to be behind one of the remaining doors. Anyway, the contestant was then given the opportunity to change his guess. The Monty Hall Problem is should he change his or her guess?