Beneath the glitz and glamour of flashing lights, free drinks and slot machines, casinos stand on a bedrock of math, engineered to slowly bleed patrons of their cash. Despite this, the casinos continue to rake in billions of dollars each year for the companies, investors and Native American tribes that own and operate them. In addition, state and local governments reap huge revenues in taxes and fees from casino operations.

While the odds for various casino games vary, most have a house edge that makes it mathematically impossible to win more than you lose. This explains why a casino will offer you comps (free goods and services) like hotel rooms, meals, tickets to shows or even limo service and airline tickets if you’re a big spender. It also explains why you should always expect to walk out of the casino with less money than you came in with.

Although the exact origin of gambling is unknown, it is generally believed that some form of it has been practiced throughout history. It is perhaps most well known to modern audiences through movies and television portrayals of casino life. From the dazzling Las Vegas Strip to the illegal pai gow tables of New York’s Chinatown, the gamblers of the world are drawn to casinos for entertainment that is both thrilling and risky. For this reason, gambling has become one of the world’s most popular activities. In fact, in the United States alone, patrons visit more than 100 million casinos each year.