The history of the game begins more than 300 years ago, at the end of the 17th century, with Frenchman Blaise Pascal being credited with this invention. Apparently, he was trying to create a perpetual motion machine as he was studying probabilities, but the outcome took him by surprise. The roulette wheel gained a lot of traction relatively quickly and by the end of the century, it was a popular game in Paris.
On an American wheel, there are 38 spots: numbers 1-36, plus 0 and 00. Your odds of winning a one-number bet are 37 to 1 (37 ways to lose, 1 way to win). But if you win, the casino doesn't pay you 37 to 1, they pay you less: 35 to 1. The difference between the true odds and what they actually pay you is 2/38, or 5.26%. You can do this same calculation for the other bets, and it comes out the same.