A progressive jackpot is a top prize that grows with play. A small share of every qualifying stake is added to the prize pool, so the amount on display keeps rising until someone wins it; it then resets to a guaranteed starting value, known as the seed, and begins climbing again. A fixed jackpot, by contrast, always pays the same amount.
Progressives come in three main forms. A stand-alone jackpot is fed by a single machine or game. A local, or in-house, jackpot links several games within one casino or brand. A wide-area jackpot pools stakes across many casinos, which is how network titles such as Mega Moolah have produced multi-million prizes.
For operators, local jackpots are a retention tool they can shape themselves, while network jackpots offer headline prizes that a single casino could not build alone. Either way, contributions, seed values and win conditions belong in the game rules.