Making sense of "What are slot bonuses?" 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 ask about them.
A few questions come up about what happens behind the scenes. When a slot machine is reset after a jackpot or a fault, nothing about its odds changes; the generator keeps running. When a machine malfunctions, the rule printed on most games voids pays and plays, and the logged result settles any dispute. Slot machines cannot be adjusted on the floor without approval and new software. Hacked machines are a rare crime, not a player strategy, and old slot machines are usually scrapped or sold on to collectors.
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 software.
Bonus rounds work as games inside the game: a set of symbols triggers free spins, a pick feature or a wheel, each paid from the same return to player as the base game. Slot autoplay features run a chosen number of spins without pressing the button, with limits on losses or single wins that stop it early. The simplest way to learn slot machine features before playing is the game's own help screen or a demo version.
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.
The game's help screen explains every feature, and a free demo shows them in action, which is the simplest way to learn a machine before staking.
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.
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.