What is a moneyline?
A moneyline is a bet or market on which side wins outright, without applying a point spread.
The short version
A moneyline asks one basic question: who wins? There is no point spread. If you choose the team or player that wins outright, the moneyline position wins, subject to the market's rules.
Favorites and underdogs
The favorite usually has negative American odds, meaning you risk more to win 100. The underdog usually has positive odds, meaning you can win more than you risk if the underdog wins.
Why odds differ
Moneyline odds reflect implied probability, market demand, fees or vig, injuries, matchup factors, home field, weather, and news. The line can move as new information arrives.
Moneyline vs. spread
A spread adjusts the score by a handicap. A moneyline only cares who wins. Favorites are easier to win outright but pay less; underdogs are harder to win but pay more.
Prediction-market angle
In prediction markets, the same idea may appear as a contract that pays if a team wins. Prices can be translated into implied probabilities, but fees and settlement rules still matter.