Once upon a time, when slots had one arm and three reels with symbols, the odds of winning had to do with the number of times each symbol appeared on each reel. But those types of odds went the way of the mechanical slot and now, with video slots and online slots ruling the roost, computers have taken over. In modern slot machines, the outcome of the game is determined by the Random Number Generator (RNG) imbedded in the machine's software.

Because the old slot machines are often perceived as the best slot machines, modern slots often have the external look of the slots of yesteryear, but that's where the similarity ends. In reality, the inner workings of the modern slot machine is what it's all about — the outcome of each spin is determined by the computer resting in the machine's belly and not by the motion of the reels themselves. But even though the computer tells the reels where to stop, the games are not pre-programmed to pay out at a certain time. The RNG at the heart of the computer ensures that each click of the mouse or tap on the screen has an equal chance at hitting the jackpot. In other words, the RNG is what makes online slots games random and fair.

Whenever a slot machine is up and running (even in between actual spins), the RNG is continually generating random numbers, at a rate of hundreds or maybe thousands per second.

As soon as the "Play" button is pressed, the RNG stops and determines where the online slot machine reels stop. This means that the results vary depending on exactly when the "Play" button is pressed. A fraction of a second earlier or later, and the result would be different. This means that if the person after you hits the jackpot, it doesn't mean that if you would have gone another round, you would've won in his place. The emphasis in RNG is most definitely on "random." When you're engrossed in online slots gambling, it is important to keep this in mind.

Slot machines are typically programmed to pay out 82% to 98% of the money that is bet by players. The winning patterns on slot machines, the amounts they pay, and the frequency with which they hit are determined so as to give a certain percentage of the money to the house or online casino, while returning the rest to the players over the course of millions of spins. What this means is that although the outcome of each and every spin is, indeed, random, the overall payout percentage (the payout over the long run) is pre-determined. In other words, a given online slot machine is never "due to hit," nor can it be considered tight or loose, hot or cold. Since the payback percentages are figured over the very long term, anything can happen (a long dry spell or two quick wins in succession, for instance) during that period. This is what makes online casino gambling so full of surprises — both good and bad.

What the existence of the random number generator means is that luck is the biggest factor of all in winning at slots. It is probably a good idea to check the payback percentages of your online casino in order to know your overall chances when you play the slots. But really what you should be looking for is Lady Luck lurking in the corner. She's your muse and savior when you hit the slots.