How to Read Betting Odds: What do the + and - Mean in Betting

+ means underdog (shows profit on a $100 bet) and - means favorite (shows how much you must risk to win $100); on point spreads the sign can refer to points instead of payout.
You’ll see -110 a lot — bet $110 to win $100 — and that extra $10 is the sportsbook’s vig; when both sides are -110 the market is basically a coin flip.
Odds encode implied probability (convertible to decimal/fractional); if your estimate of an outcome is better than the implied chance, the bet has value.