Odds and prices
What is a sports betting line?
A line is the number the book attaches to a game to make both sides of a bet roughly equal. It can be a handicap on the score, a total for combined points, or just a price on the winner.
The line exists to balance the market, not to predict the game.
The three kinds
A spread gives one team a head start on paper. Take the favourite at −1.5 and they have to win by two.
A total sets a combined score and you pick over or under. Half-points exist so there is no tie to settle.
A money line skips the handicap and prices the winner directly, which suits sports where scoring is low and margins are thin.
Why the number moves
Money is the main driver. Weight of stakes on one side moves the number until the other side looks attractive enough to bring balance.
Information moves it too: a lineup change, a rest situation, weather in an outdoor sport. Books reprice quickly, and the amateur is almost never first.
A line that moves against the obvious side is worth noticing. It usually means larger accounts have taken the other one.
Locking a number
The number you take is the number you keep, even if the line moves after. That is the one genuinely valuable thing about betting early, and it is also how people talk themselves into betting too early on nothing.
Some apps offer to protect a better number for a fee. Read what you are paying before you tap it. On a phone that button sits right next to the confirm, which is not an accident.