What is a betting line?
A betting line is the book's offer on a game: the number you are betting against and the price you pay to bet it. In the trade we just say the line, or the number.
Three numbers on the board
Most games come with three lines, and a sports betting line is easiest to read once you see them side by side. Say the board shows this:
| Team | Spread | Moneyline | Total |
|---|---|---|---|
| Chiefs | -3 (-110) | -150 | Over 47.5 (-110) |
| Bills | +3 (-110) | +130 | Under 47.5 (-110) |
The spread says the Chiefs have to win by more than 3 for a bet on them to win, and the Bills can lose by up to 2 and still cash a bet on them (lose by exactly 3 and it's a push). The -110 next to each side is the price: you lay $110 to win $100. The moneyline drops the points and asks only who wins, with the favorite at -150 (lay $150 to win $100) and the dog at +130 (bet $100 to win $130). The total is a bet on the combined score, over or under 47.5.
So when someone asks what the line is on a game, they usually mean the spread. When a bettor says he got a good line, he means the number and the price together, because the two are one offer. The spreads, moneylines and totals each have their own page.
Where the line comes from
A line is not a prediction of the score. It is the number the book thinks will get bets on both sides, with its cut built into the price (the line-setting page covers how it's made). Look at the moneyline above. At -150 the Chiefs need to win 60 percent of the time to make the bet break even, and at +130 the Bills need 43.5 percent. Add them and you get 103.5 percent. The extra 3.5 is the book's margin, and that's the part of every line I'd want a new bettor to see first.
Lines move
The line you see on Tuesday is rarely the line at kickoff. It opens, money comes in, news comes out, and the book moves the number or the price. Bet the Chiefs at -3 and the line goes to -4 before the game, and your ticket still says -3. That is why sharp players care so much about when they bet and where, and why I'd look at two or three books before taking any line. The difference between -3 and -3.5 at the same price is worth more than most people think, and why odds move explains what pushes them.
A line is just an offer. You don't have to take it, and the best bettors pass on most of them.
Related questions
How do betting odds work?
Betting odds are a price. They tell you what a bet pays and, read the other way, how often it has to win. Odds of -200 mean you risk $200 to win $100. Odds of +150 mean you risk $100 to win $150.
What does the spread mean in betting?
The spread is a head start the book gives the underdog to make the game an even bet. A team at -7 has to win by more than 7 for a bet on it to win. A team at +7 wins the bet if it wins the game or loses by fewer than 7.
Why do odds move?
Odds move because the book's risk changes or the information does. Money moves a line, most of all money from bettors the book respects. So do injuries, weather and what the other books are dealing.