Roulette has lots of variations, but the most popular suggests the European one.
Roulette is played with a board, consisting of 36 red and black numbers, and zero, and a spinning roulette wheel with numbers in partitions around the edge.
Players place their bets either on distinct numbers or on combinations (inside and outside bets).
The croupier spins the roulette wheel in one direction and the ball into the wheel in the opposite direction.
As the ball spins in the wheel, it will slow down and eventually fall into one of the numbered partitions.
The number it falls on is the winning number, and anyone who has bet on that number wins.