The term 'Bingo Square' is a term used to describe a game of chance, similar to Bingo. It is played on a grid of squares, with each square containing a number or letter. Players mark off the squares when the corresponding number or letter is called out. The term 'FREE' is used to describe a square that does not need to be marked off, as it is already considered to be marked off. This square is usually located in the center of the grid and is often referred to as the 'FREE square'.