We monitor several of the casinos in Las Vegas for sports book betting and average out their predictions.
The Over/Under is the predicted total score for both teams. For example, if the Over/Under was 42, that means that Vegas believes the total points scored by both teams will be equal to 42 (example: Team A scores 22 points and Team B scores 20 points).
The Spread is the predicted difference between the scores for both teams. For example, if the spread was 7, that means that Vegas believes that the winning team will score 7 more points than the losing team.