In case no one has told you this, the days of the classic slot machine are gone. Slots today are a variation of a video game. No longer are you pulling the handle to set the reels in motion. Now the handle on your favorite slot machine is nothing more than a classic-feeling accessory to make you feel like you're playing a slot machine from the day of yore. Old style slot machines do exist, but they are just an example of technology that is past its prime. The slot machines of today are intricate works of technological art, combining the game play of classic slot machines with multiple lines and a number of bonus options and other features which would have been unimaginable on a classic machine.
One of the most important concepts of the video slot machine is the random number generator, also known as the RNG. The RNG is the little device in the slot machine that makes sure the slot is always giving you a random outcome when you play. If it weren't for the RNG, it would be plausible that someone could program a slot machine to never win. It wouldn't be a very nice thing to do from a player perspective, but it would make nice money for a while.
The RNG basically works like this: all day, every day the RNG sits there throwing out random numbers faster that imaginable. When a person puts the initial coin in the machine or hits the spin button (depending on the machine) the RNG stops. The numbers that are there determine what your spin will produce.