Progressive slots are games which are the most popular with players and profitable for the casinos. These are the games with a progressive jackpot as the top win. The progressive jackpot grows every time a player at any online casino all over the world plays that progressive slot. It happens because a small share from every bet goes to the progressive jackpot. Since players can play the same progressive in different online casinos the jackpot grows very quickly until someone hits it. You can see the current size of one or another jackpot over the slot reels. Most progressives have definite rules for players to follow in order to be eligible for the progressive jackpot. However, to tell the truth, the odds of hitting a progressive jackpot are quite low.