Progressive slots are slot machines that accumulate towards a further jackpot over and above any amount that you could 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, and the progressive slot wager portions from all of these sites are centrally pooled to make up the grand jackpot, which may be won by playing online gambling agent at any of these sites. At land-based casinos the same principal applies, the main difference being that a number of physical 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 types 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 individual machine shall pay out.