There are a few things that go into how Bingo balls work. First, the ball is covered in various numbers and letters that are randomly placed on the surface. Second, there is a light inside of the ball which flashes when it is picked up. This causes the numbers and letters to be projected onto the walls or ceiling of the bingo hall.
Finally, a machine reads the projected numbers and letters and sends them to a computerized system to be counted as a win or loss. In order to make sure that everyone has a fair chance at winning, Bingo balls have certain numbers (like 2s) that do not appear often on the playing surface.
