The Steelers are a +3 underdog against the 49ers. Let's use a 2023 NFL Week 1 game as an example. The worse team (the underdog) can lose by fewer than that same amount of points, or just win the game.
The perceived stronger team (the favorite) must win by a certain number of points/runs/goals to cash your bet. It's the most popular bet type in basketball and football. A point spread is simply a bet on the margin of victory.
