A slot is an opening or notch in a surface. In ornithology, it is a narrow gap between the tips of the primaries of certain birds, which during flight helps to maintain a smooth flow of air over the wings.

The slot in a machine is where a coin or paper ticket is inserted into a slot, or in “ticket-in, ticket-out” machines, a barcoded paper that is scanned as the machine is activated by a lever or button (physical or on touchscreen). Once activated, the reels spin and stop to rearrange symbols based on the paytable and a random number generator (RNG). If a winning combination is found, the player receives credits according to the game’s rules. The symbols vary depending on the theme, but classic symbols include fruits and stylized lucky sevens. Most slots have a specific theme or style, and bonus features & payouts are often aligned with the theme.

The coloured boxes in the pay table display where the symbols have to land to trigger different payout values. This area may be permanently displayed on the machine, or it may be available through an interactive series of images accessed via touchscreen. Depending on the size of the display, all possible combinations may not be visible – especially when a progressive jackpot is involved.