When you play table games in a land based casino, you can easily see that they are games of chance and where the element of uncertainty comes from because the physical processes and aspects of the games.
Take roulette for example. After the wheel is spun, its completely uncertain where the ball will drop. Or if playing a card game, after the deck has been shuffled which cards will be dealt to you. Or if you play craps, the dice are supposed to bounce the dice against the edge of the table making it unpredictable which numbers will land face up. But when you play these casino games online, none of these physical characteristics are present. And that’s why online casinos need software to introduce uncertainty into the games. The Random Number Generator (RNG) is the complex mathematical computer system (beyond my understanding!) designed to yield a random number.
In the case of slot machines, it is the RNG that determines the outcome of each spin. It generates numbers to correspond to symbols on the reels of the slot machine. Misunderstandings of how RNGs work has lead to all those myths and misconceptions out there about slot machines payout cycles. The numbers produced by the RNG are unpredictable and unbiased.