More than 50 million people—that’s a quarter of the world’s population over 21—visit casinos each year. The number includes both domestic and international travelers. Casinos are the most popular gambling destinations, but they also offer a range of other amenities such as restaurants, spas and golf courses.

Despite the glitzy perks, there are some things every casino patron should know. For example, most casino employees are not allowed to gamble on the premises. The rule applies to workers in the hotel, food service, golf course or convenience store as well as gaming-floor staff.

Many casinos are located in tourist destinations, and their owners realize that location is key. The elegant spa town of Baden-Baden in Germany’s Black Forest began as a playground for European royalty and aristocracy 150 years ago, and its casino is still considered one of the most beautiful in the world.

Casinos are legal in most countries, but regulations vary. In the United States, many states changed their laws in the 1980s to permit casinos, and many American Indian reservations have casinos.

Casinos are designed to make money, and they do so by offering odds that are uniformly negative from the player’s perspective. This is called the house edge, and it exists in all games. Some casinos, such as poker rooms and video poker machines, have an additional disadvantage built into them: The casino takes a percentage of the money played, which is known as the rake. This makes the game less profitable than it could be.