Many players believe that the reels are physically spinning and "landing" on a result. In reality, the outcome of every spin is decided the exact millisecond you press the spin button. The visual animation of the reels slowing down is simply a presentation designed to build excitement; the result already exists in the system before the first reel even moves.
This is made possible by the Random Number Generator (RNG). The RNG is a complex algorithm that generates a continuous stream of random numbers. When you click spin, the game picks the current number from that stream and maps it to a specific combination of symbols on the reels. Because the RNG never stops, every spin is a completely independent event. This means a game does not "know" if it has paid out recently or if it has been quiet for a long time; the odds remain identical for every single click.