When most people think about gambling, they think about a casino. But what is a casino? According to Merriam Webster's dictionary, a casino is a "building or room used for social amusements, specifically gambling." This definition is much broader than what the average American would consider a casino to be. Most people would picture one of the megaresorts in Las Vegas—a massive hotel and entertainment complex, blazing with neon lights, fun, and games. While this description does fit some casinos, many others are small businesses defined more by the types of gambling they offer than by glitz and glamour.

The federal government classifies all businesses and industries operated within the United States with a six-digit code called the North American Industry Classification System (NAICS) code. The NAICS code for casinos is 713210. The official definition of code 713210 is as follows: "This industry comprises establishments primarily engaged in operating gambling facilities that offer table wagering games along with other gambling activities, such as slot machines and sports betting. These establishments often provide food and beverage services." Casino hotels fall under NAICS code 721120. These are hotels with a casino on the premises. They typically offer a variety of amenities, including dining, entertainment, swimming pools, and conference and convention rooms.

For practical purposes, casino gambling encompasses games of chance and skill played at tables and machines. Therefore, casino games take place in massive resorts, as well as in small card rooms. There are floating casinos operating on boats and barges on various waterways across the country. Casino game machines have been introduced at racetracks to create "racinos." Also, some casino game machines are allowed in truck stops, bars, grocery stores, and other small businesses. By and large, the industry is composed of land- and water-based gambling halls that offer both table games and slot machines.

Like any industry in a capitalist society, casinos are in business to make money. Successful ones rake in billions of dollars each year for the companies, corporations, investors, and Native American tribes that own and operate them. State and local governments also reap casino revenues in the form of taxes, fees, and other payments.