Asked as "What RTP stands for?", the answer starts with one ticket. A parlay, called an accumulator in many places, joins several picks into one bet. Every leg has to win for the ticket to pay, and the odds of the legs multiply, so a small stake can return a large sum. What makes the format attractive is the same thing that makes it hard: each added leg lowers the chance that the whole bet lands.
A parlay works by multiplication. Each leg carries its own odds, and the payout on a parlay is the stake times the decimal odds of every leg multiplied together. Three legs at 2.0 each turn one unit into eight. The same arithmetic runs the other way for the chance of winning: three picks that each land half the time win together only one time in eight, and the price offered usually pays less than that fair eight.
Several types of combination bets soften the all or nothing rule. A round robin splits a list of picks into every smaller parlay, doubles or trebles, so one loss does not end every ticket; round robin bets cost one stake per combination. An anti accumulator bet reverses the logic and pays when at least one leg loses. Systems with names like trixie or yankee are round robin bets with fixed sizes and a fixed count of lines.
An accumulator bet is the same idea under another name. To place one, a bettor adds selections to a single slip, picks the accumulator or multiple option and enters one stake for the lot. How does an accumulator bet work when a leg is called off? The void leg drops out and the rest stand at reduced odds. A lost leg ends the ticket at once, whatever the other results turn out to be.
The whole ticket is lost at once, whatever the results of the other selections turn out to be.
Picks from one match are linked, so the book prices the combination as a whole and usually applies a wider margin than on separate games.
Multiply the stake by the decimal odds of every leg; three legs at 2.0 each turn one unit into eight.
Most books drop that leg from the ticket, and the parlay pays at reduced odds on the legs that remain.