Prop Bet
A wager on a specific occurrence within an event that is not tied to the final result or main spread, such as a player's stats or the number of corners.
Definition
A proposition (prop) bet targets a particular event within a game rather than the overall outcome: a player to score, total corners or cards, first team to a milestone, or a novelty market. Props range from statistically driven player markets to pure-luck novelties, and they typically carry higher bookmaker margins and lower stake limits than main markets because they are harder for the book to price and easier for informed bettors to attack. They are hugely popular for big events.
Worked example
A book prices 'Player X over 22.5 points' at decimal 1.90 (implied 52.6%) and 'under 22.5' at 1.90 as well; the two prices sum to 105.3%, so the 5.3% overround is the book's margin on that prop.
Why it matters
Props introduce beginners to markets beyond win or lose, and specialists find soft, less-efficiently-priced player props among the few areas where an edge can persist, until limits shut it down.