A slot is a space or position in which something can fit. In a slot game, the symbols appear on the reels and, if they match up in a winning combination, the player earns credits according to the paytable. Many slots have a theme, and the symbols and bonus features are aligned with that theme. Some states allow private ownership of slot machines; others prohibit it or restrict the type that may be purchased.

In modern electromechanical slot machines, microprocessors assign a different probability to each symbol on every reel, allowing the machine to appear to pay out when it is “close” to a winner. This is known as “taste,” and it keeps players seated and betting, even when the odds are long against making a profit. The microprocessor also allows the machine to detect and correct many types of malfunctions, such as a door switch in the wrong state or an out-of-paper sensor. Such malfunctions are still sometimes called a “tilt” by dealers, from the fact that electromechanical machines used to have tilt switches, which would make or break a circuit when a machine was tampered with.

A jackpot is a large prize pool that accumulates during a period of time before the winnings are distributed. The term jackpot entered the English lexicon via a 19th-century poker variant that required players to declare a hand with a pair of jacks or better to open bidding. It then grew in popularity to refer to any large prize, particularly in gambling.