Roullete is a casino game in which bets are placed on the outcome of a spin of a small ball on a revolving wheel. The wheel has numbered compartments (called canoes) alternately colored red and black. There is also a green compartment with the number zero on European roulette wheels and two such compartments on American roulette wheels.

When the wheel stops and a number is announced, players place their bets by placing chips on the betting table that correspond with the numbers on the wheel. The chips are not returned to the player unless requested; they remain their property and may be used on other spins. Various systems have been devised for beating the game, but none is foolproof and all require large bankrolls to be effective.

During a spin, the ball bounces around the wheel in a random manner and ends up in one of the compartments as it comes to rest. The odds of hitting a specific number vary depending on the type of bet made. For example, a straight-up bet on a single number pays 36 to 1 while the odds of hitting the second dozen are only 2-1.

A player wins a bet only if the ball rests in their selected compartment and loses if it hits any other. Some bets have a symmetrical structure, such as the column bet, which covers 12 numbers in three columns on the betting table and is therefore easier to win than other bets.

The game was invented in the 17th century by the French mathematician Blaise Pascal as he experimented with perpetual motion machines. He is alleged to have been inspired by the Chinese game of hoca and the earlier games hoca portique and rouleau. The modern game is widely played in casinos and gambling houses throughout Europe and in the United States.