A casino slot machine is one of the most popular casino games. Traditional slot machines are coin-operated machines with three or more reels. They spin when a lever on the side of the machine is pulled. The machines include a currency detector that validates the coin or the cash inserted to play. The machine typically pays off based on patterns of symbols visible on the front of the machine when it stops. Modern computer technology has resulted in many variations on the slot machine concept. Currently casino slot machines are the most attracting gambling method in casinos and they generate about 70% of the average casino's revenue.

Along with online casinos, online betting websites are a great attraction on the Internet, drawing thousands of bet enthusiasts and casino game players every day. According to a series of recently conducted surveys which involved the participation of around 3000 regular betters and casino game players in thirteen countries, online betting and online casinos are the primary option for gamblers worldwide. Among the 3000 surveyed persons, more than 85 percent claimed to prefer online betting and casino games over their traditional, offline counterparts. Furthermore, while 60 percent of the persons who regularly play casino games online stick with free games, the other 40 percent play for real money.