Progressive slots are slot machines that accumulate towards a further jackpot over and above any amount that you may actually win on the equipment. A small portion of each player's bets go towards this jackpot. Hundreds of online gambling sites offer the same progressive slots, as well as the progressive slot wager portions from all of these sites are centrally pooled to make up the grand jackpot, which can be won by playing at any of these sites. At land-based casinos the exact same principal applies, the difference being that a number of physical professional slot machines are linked together to form a progressive slot machine network, paying out a progressive slot jackpot beyond the payouts that each machine makes to players on their own.

There are 3 kinds of progressive slot machines in real-world casinos. Independent progressive slot machines are not linked to other machines, but a portion of each bet is still taken and put towards a "super" jackpot that the person machine will pay out.