Making sense of "3 reel slots" starts inside the cabinet. A slot machine looks like a game of reels, but what decides every payout is a random number generator working out of sight. The reels, the paylines and the buttons on the screen only show a result that was fixed the moment the spin began. Knowing how that works, from mechanical machines to modern video slots with megaways and bonus rounds, clears up most of what players wonder about them.
Older mechanical slots work with physical reels and a coin mechanism: a coin drops past sensors that check its size and weight, a lever or button releases the reels, and stops on each reel decide the symbols. Class II slots, found in some venues, work differently again: each spin is really a round of bingo against other players, and the reels simply display the outcome of that draw in a familiar shape.
Slot machines determine a payout in two steps. A random number generator picks a result the instant the spin button is pressed, and the pay table converts that result into a win or a loss. Slots are actually random in this sense: no spin remembers the last, and a machine is never due. What the operator sets is the return to player, the share of stakes paid back over millions of spins, which is fixed in the game's code.
Paylines on a slot machine are the patterns across the reels that count as a win, from a single middle line on classic games to hundreds on modern ones. Megaways games change the number of symbols on each reel every spin, giving tens of thousands of ways to win. The buttons set the stake and the number of lines. Which type of slot machine is best depends on what a player wants: steady small wins, or large ones that come rarely.
Return to player, the share of stakes paid back across millions of spins, is chosen by the operator and fixed in the game software rather than adjusted between spins.
Free spins, pick features and wheels are games inside the game, funded from the same return to player as ordinary spins rather than from anything extra.
Autoplay runs a chosen number of spins automatically, and limits set on total losses or on a single large win halt it before the count runs out.
A reset after a jackpot or fault leaves the odds untouched, while a malfunction voids pays and plays under the printed rule, with the logged result settling disputes.
Paylines are fixed winning patterns, from one middle line to hundreds, while megaways games change the symbols on each reel every spin to create tens of thousands of ways.
Each spin on a Class II machine is really a round of bingo against other players, and the reels simply present that draw's result in a familiar form.