If you're a beginner in sports betting, the two things you want to understand are the odds and the terminology. The terminology begins with the spread.
Margin of victory set by oddsmakers to get bettors to place bets on both the favorite and underdog
For example: Team A is playing Team B, the point spread is 4.5. If Team A is the favorite (supposed to win), a bettor may bet the spread for Team A, meaning Team A must win by MORE THAN 4.5 points (also known as -4.5). This means that Team B is the underdog and if a bettor wants to bet the spread for Team B, Team B must win or lose by LESS THAN 4.5 points (also known as +4.5)
This IS NOT choosing the winning team, this is "betting the spread"
The advantage of betting the point spread is that you can bet on an underdog, but that underdog doesn't need to necessarily win. As long as they lose by less than the point spread, the bettor will still win their bet
On the flip side, this makes betting on a favorite more difficult but more profitable.
Normally odds when betting on a spread is -110 (bet $11 to win $10), which is better odds than betting on a 4.5 point favorite to win straight up, which would be odds of around -175 (bet $17.50 to win $10)