A thin opening or groove, especially one in something that can be used to insert or remove items. You might put letters and postcards through the mail slot in a door, or insert money into the coin slots in a casino. There is a wide variety of slot games, including video poker, fruit machines, and traditional reel slot machines. Some have wild symbols that substitute for other reel symbols on a pay line to increase your chances of winning. They also come with multipliers to give you extra payouts.
The odds of hitting a jackpot are determined by a random number generator, a computer algorithm that calculates the probabilities of each possible outcome. Once the machine reads a win or loss, it stops spinning and displays whether you have won or lost. Some machines are programmed to always pay out a certain percentage of the money that is deposited. Those are called high-return games and generally cost more to play.
Conventional mechanical slot machines gave way to electrical ones that worked on similar principles but had flashier displays and automated money-handling systems. They still needed a way to determine who won or lost, however.
Pay tables were once directly printed on the machines themselves, but now they’re often embedded in online help screens. They list all the different symbols in a game and how much you can win for landing (typically) three, four or five matching symbols on a pay line. The tables are usually shown in coloured boxes to make them easier to read.