About 51 million people—a quarter of all those who are 21 or older in the United States—visited a casino last year. And while dancing fountains, dazzling hotel rooms and upscale restaurants all help draw people in, it’s games of chance that drive the billions in profits casinos rake in each year. Slot machines, blackjack, roulette and craps make up most of that, although there are a few other games, such as baccarat, keno and poker, in which skill can play a part.

While some players may have a gift for the game, most people who gamble aren’t lucky enough to walk away with a jackpot. Even the most experienced and skilled players must accept a certain percentage of losses, known as the house edge. And while the odds are stacked against them, casino owners can still turn a profit.

Security at a casino starts on the floor, with employees keeping their eyes on the tables and patrons to spot anything that doesn’t look right. Dealers, who are heavily focused on their own game, can often spot blatant cheating such as palming or marking cards or dice. But casino managers and pit bosses have a broader view, monitoring the betting patterns of players to see if any are suspicious.

The use of technology in casino security has increased dramatically over the past few years. For example, casinos now routinely monitor their roulette wheels electronically to discover any statistical deviations from the expected results. Casinos also track player behavior using video cameras and computer systems. This information can be useful for security, but it also helps improve the games themselves.