Short, plain answers to the questions people actually ask about parlays and prop research — written to be read once and understood, and to say where each number on this site comes from rather than asking you to take it on trust. Nothing here is a pick.

Parlay basics

• What is a parlay? — A parlay is one bet made of several selections that must all win. How the odds combine, what a 2-leg and 3-leg parlay mean, and why the sportsbook’s margin compounds with each leg.
• Same game parlay, explained — A same game parlay combines legs from one game. Why those legs do not settle independently, why the book’s price is not the multiplied price, and what the builder does about it.
• What is a player prop bet? — A player prop is a bet on one player’s own numbers, settled from the box score rather than from who won. The kinds, what happens when the player does not play, and what to check first.
• Moneyline, spread and total — The three bets almost every game offers: who wins, by how much, and how many points are scored. What each one settles on, and why a favourite can win and still lose the bet.

Reading a number

• American odds explained — What a minus price and a plus price mean, how to turn either into an implied probability, and why the two sides of a market add up to more than 100% — the sportsbook’s margin, in plain arithmetic.
• How to read a player prop hit rate — Games cleared over games played, at one threshold, over one window. What a small denominator hides, why a short window flatters, and why the threshold should come from the player rather than the book.
• Over/under betting explained — An over/under is a number the book sets and you take a side of. What the line is for, why it ends in .5, what a push is, and why a line moving is not the book changing its mind about who wins.
• Why sportsbooks post different odds — The same selection is rarely priced identically at two sportsbooks, and the line itself can differ too. Why that happens, what comparing prices does, and what it cannot do.
• MLB strikeout props — Why a pitcher’s strikeout market only appears once he is announced, why both sides are usually posted, and why a strikeout log counts appearances rather than starts.

Tools, explained

• What is an AI parlay generator? — An AI parlay generator assembles a multi-leg ticket from a scored board instead of a hunch. What it can and cannot know, and what to check before trusting one.
• What is a prop builder? — A prop builder is the tool for assembling one player-prop selection: pick the player, the stat and the line, then check how often it has actually happened and over how many games.
• What is a bet builder? — Bet builder is the sportsbook name — mostly UK and Irish — for combining several selections from one game into a single ticket. What it is, what it is called elsewhere, and how it is priced.

Prediction markets

• Parlays on Polymarket, explained — Polymarket trades event contracts, not sportsbook parlays. What that difference means, what combining contracts does and does not do, and how the venue’s posture differs from a book.
• Kalshi parlays, explained — Kalshi is a CFTC-regulated event-contract exchange, not a sportsbook. Why combining contracts there is not a parlay, and how that changes what a price means.

The season

• The sports betting calendar — Which leagues are in season month by month, when player props are posted, and what an off-season board looks like — so a quiet slate reads as the calendar rather than a broken page.

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Odds and lines come from licensed data feeds and refresh on a schedule; hit rates, edges and grades are Parlay Builder’s own calculations.