A slot is a narrow opening. People put letters and postcards through the mail slot at the post office, for example. A slot is also a place or position, like the space in between linemen and wing-wideout on a football team, or the area of ice hockey where the short-stop lines up to protect the goal. In computer science, a slot can refer to an expansion port or the space in a motherboard where a CPU sits. A slot can also refer to a software setting or feature that allows people to change the way they play a game.
A common superstition in slots is that a machine that has been “due” to hit will make up for its long losing streak by paying off big on the next spin. But this is a myth, because microprocessors inside modern slot machines randomly assign different probabilities to each symbol on each reel. If a particular machine has gone long without hitting, this does not mean that it is due to pay out soon; the odds of any given combination occurring on the next spin are no different from the odds of any other combination.
A better strategy is to look for a slot that has recently won. This will be obvious, as the amount of the cashout will be displayed next to the number of credits in the machine. This information is available at many brick-and-mortar casinos, and can be found online as well.