A casino is an establishment for gambling. It is also known as a gambling house or a gaming hall. In the United States, casinos are regulated by state law. Various jurisdictions have different laws concerning the types of gambling allowed, and some ban some forms altogether. Casinos vary in size and architecture, but all are designed to maximize profits from wagers.

Casinos depend on patrons to generate revenue and profit, and thus are vulnerable to cheating and theft by both employees and patrons. Therefore, many casinos have strict security measures to protect against these activities. These may include a physical security force that patrols the premises, and a specialized department that operates a closed circuit television system (CCTV) that monitors activities within the casino floor through one-way glass.

The largest and best known of these casinos are located in Las Vegas, Nevada, and Atlantic City, New Jersey, which share the distinction of having the highest per-capita revenue of all casino cities in the world. Other major casino cities include Monte Carlo, Monaco; Paris, France; and Macau, a special administrative region of China.

Most casinos offer a variety of games of chance, and some offer a small amount of skill. The most popular games are slot machines, which make up the largest proportion of casino revenues. These machines accept coins or paper tickets with barcodes, and display bands of colored shapes that roll on reels—either real mechanical reels or a video representation of them. When a winning combination is displayed, the player receives a predetermined sum of money.