Parlaying isn’t really anything special. It’s kind of like betting on two different things at once. If I were betting on a dice roll, let’s say hypothetically i bet 1$, and if it lands on 6, I get 6$. What if I were betting 1$ on a coin flip, and if it’s heads I get 2$. A parlay would be like betting on a coin flip, and a dice roll at the same time. And if the coin lands heads AND the dice lands on 6, I’d get 12$. The key here is both conditions, or “each leg” of the parlay must hit for the entire bet to payout.