With online casinos offering a whole host of different roulette variations these days, it is typical to find both types of game available. Players from North America and other US-leaning regions will typically find a wheel with the same 36 red and black numbers but with two green sections, a zero and a double zero, so 38 possible options for the ball in total.
As a generalisation and certainly traditionally speaking, players in the UK and Europe will be accustomed to a roulette wheel with 37 sections: numbers one to thirty six and a single, green zero.