A jackpot headline tells you how much; it rarely tells you how. The difference between a fixed and a progressive prize is not just size, it is the source of the money and what that implies for everything else about the game.
Fixed jackpots
A fixed jackpot is simply the top entry in the paytable: a specific multiple of your stake, say two thousand times the bet, paid when a particular combination lands. The sum is funded from the game's ordinary payout budget, which is why fixed-jackpot slots can still offer a normal return to player figure across the rest of the paytable. The prize scales with your stake. Bet twice as much and the fixed jackpot doubles. Nothing accumulates between players and nothing is shared across sites.
Progressive jackpots
A progressive takes a small slice of every bet, often around one or two per cent, and adds it to a pool. The pool grows until someone wins it, then resets to a seed amount that the provider or operator funds in advance. Two shapes exist. A local progressive collects only from players at one operator. A networked progressive pools across every casino running that game, which is how the famous multi-million figures are reached. At WinnerIsland Casino the jackpot counter you see on a networked game is the same number every other site shows, because it is one pool.
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The contribution has a cost. If two per cent of each spin feeds the jackpot, the base game pays out two per cent less than it otherwise would. In practice you are buying a lottery ticket with part of every bet, and the ticket only pays if you are the one player out of millions who hits it.
Reading the fine print
Three details matter. First, whether the maximum bet is required to qualify for the top prize; some games pay the progressive at any stake, others only at the top level. Second, whether the jackpot is paid as a lump sum or in instalments, which is rare now but still appears. Third, the seed value, since a jackpot that has just reset is mathematically identical to one that has grown, but feels very different.
A reasonable approach: treat progressive play as entertainment with a tiny lottery attached, not as a strategy. Jackpot games are for adults only, and the counter ticking upwards is designed to be watched.