Way back when there used to be an Italian card game called Biribi. This game became popular in France and from this popularity the version of the game was born, called “Little Wheel”, or “Roulette” in French.
The game of Roulette involves a spinning wheel with slots around the edge. The edge of the wheel is tilted with a circular tracking round around it and along this track there are slots which are all marked with combinations of colours and numbers. The colours are red or black and numbers are either low (1-18) or high (19-36). The number of slots can differ depending on the version of the game. French or European style roulette has thirty seven (37) slots, American style Roulette has thirty eight (38) and Sands Roulette has thirty nine (39).
The Roulette wheel is operated by a member of casino staff called a Croupier, who at the start of each game will spin the Roulette wheel in one direction. Once the wheel is spinning with momentum, the Croupier will take a small white ball, which is conveniently sized to fit inside the slots in the outer, tilted track at each colour/number marking. The ball is spun into the wheel in the opposite direction.
The ball will spin and bounce around the track, passing through an area of deflectors before eventually losing momentum and settling on the outer tracking and falling into one of the colour coded and numbered slots.
Anyone who has placed a bet against the correct landing slot can then collect their winnings.