A slot machine is a gaming machine activated by inserting money inside it (hence, "slot"). There are reels on a slot machine with symbols on each reel. If the symbols fall in line in certain ways, the machine will pay out money to the player. Normally, the rarer the spin combination, the higher the pay. If no paying spin is made, the machine simply collects the player's bets.
Progressive slots is the name given to slot machines that have rising jackpot prizes in them. While regular slots have fixed payouts for all paying spins, progressives have a growing jackpot prize for the highest spin. Each time a progressive slot machine is played, it contributes to the jackpot. The jackpot is won when a specific spin is made.
There are three kinds of progressive slots:
Single Progressive Slots are stand-alone progressive slots. The jackpot is on that slot machine only. It does not affect and is not affected by plays in other slot machines. As a result, the jackpot rises slowly.
Linked Progressive Slots are a group of slots that are connected. Every spin made in any of these machines adds to the total jackpot. So if ten machines are played simultaneously, the jackpot is incremented ten times. So the jackpot in linked machines grows bigger faster than those in self-contained progressives.
Multi-Location Progressive Slots have the biggest prizes. These slots are housed in different casinos with several hundreds of slots adding to the jackpot. To win such a jackpot is everybody's dream. But the chances are very low.
As a rule, progressive slots require you to bet the maximum number of credits to be eligible for the jackpot. But you don't have to bet the max to be able to contribute to the same. So you should always bet the max if you don't want to add to a prize that you have no chance of winning! Worse, if you bet less than required and you DO hit the jackpot, you won't be eligible for it!
If you are on a tight budget and want to bet smaller amounts, you should stick to regular machines. Avoid progressive slots if you can't afford to bet max on every spin.
Now you may ask, when is the best time to play for the jackpot? Some say it is best to play when casinos are crowded and busy. This is because the slots see the most action and the payback percentage is reached sooner. But there is no sure way to predict when the jackpot will hit.