A slot is a narrow opening for receiving something, as a coin or paper. In casino slots, it is the vertically arranged columns that hold symbols and rotate when a lever or button is pressed (or, in “ticket-in, ticket-out” machines, a barcoded paper ticket). The reels stop to rearrange the symbols and, if they match a winning combination, yield credits based on the machine’s pay table. Some slots also have special symbols that can trigger other features, such as bonus levels or progressive jackpots.
The odds of hitting a particular symbol or sequence of symbols are determined by a random number generator, which generates many numbers every second. When it receives a signal — anything from a button being pressed to the handle being pulled — the RNG sets a sequence of three numbers. The computer then uses an internal sequence table to find the corresponding reel location. The reels then stop at those placements, and the symbols on the pay line determine if the spin was a winner or not.
One of the most important things to keep in mind when playing slots is that the outcome of each spin is entirely random. Some players get caught up in the idea that a particular machine is due for a big win, but this simply isn’t true. Besides being impossible to prove, it would require the RNG to record and analyze every single spin of the reels over an extremely long period of time.