The 0 (single zero) and the 00 (double zero) are the green slots on the roulette wheel. These pockets could receive a 35:1 payout if hit straight up. If there's a split, the payout could be 17:1.
Each spin of the wheel provides a multitude of options for the player. A player may bet on single numbers, rows of numbers, or on adjacent numbers. A player also may play colors, odd or even numbers, among others. A bet on a single number pays 35 to 1, including the 0 and 00.