Roulette is a casino game where players place bets on numbers or groups of numbers, the color red or black, whether they are odd or even, and so forth. The game itself is based entirely on luck; once all the bets are placed, the dealer spins a wheel and drops a ball into one of the numbered sectors on the roulette table (aka layout). The number on which the ball lands determines who wins.
There are a lot of different theories on how roulette was invented, with some people believing it was created by French mathematician Blaise Pascal in his attempts to create a wheel that could demonstrate perpetual motion; others think the game was derived from older games like hoca and portique, while still other people believe that the game was brought to France from China by Dominican monks. Whatever the truth may be, the game evolved over time and adapted to its current form in the gambling dens and casinos of Europe and America.
Basically, the roulette wheel is a solid wooden disk slightly convex in shape, with thirty-six compartments or pockets painted alternately red and black. A fourth pocket, labelled green in European-style wheels and red in American-style wheels, carries the number 0. The compartments are divided into three dozen groups (or canoes in roulette croupier parlance) of twelve numbers each; each of these dozens is further subdivided into two or more subgroups.
Another thing to remember about roulette is that the 0 and 00 aren’t counted as either odd or even; they are purely house numbers, giving the casino an edge over the player. Because of this, any bet that includes a single number and the 0 or 00 loses. There are a few bets that offer even money, however. The Dozens Bet (called passe et manque in French) is one of these, where the player wagers that the winning number will be in the first or second dozen, or in the third; any other bet loses.
The other even-money bet is the High or Low Bet, called impair et pair in French. In this bet, the player wagers that the ball will land in the first 18 odd numbers on the layout (1-18) or the last 18 even numbers (19-36); again, any other bet loses.