Modern gaming machines use computer technology to operate their functions. Slot machine outcomes are determined unsing a Random Number Generator (RNG) which is a mathematically-based program that selects groups of numbers to determine which symbols are selected to produce a winning or losing outcome.
Slot machines are programmed to pay out a certain percentage of the money wagered over time, which is known as the "return to player" (RTP). This percentage is typically set by the casino and regulated by gaming authorities.