Some games are predictable, where everybody knows who’s going to win a particular event, a clear favourite for a championship vs a lowly underdog, or a team where you know certain key players are injured. This is not very interesting to bet on, mainly because the return on betting the favorite will not be very high at all, and the underdog is highly unlikely to win in the first place.
An example would be the following:
Miami Dolphins +2.0 -110
New York Yankees -2.0 -110
In this example, the spread is set to 2 points, the +2 means that the Miami Dolphins are the underdog in this instance, for a successful bet the Miami Dolphins must win or not lose by more than 2 points. The opposite of this is that for a bet to win on the favourites, the New York Yankees must win by more than 2 points.
If the New York Yankees win, but only by the pointspread (in this case 2) then the bet is voided and the stakes are returned.
The second number -110 indicates the return on $100 on a successful pointspread bet, so a winning bettor will win $100 for every $110 bet, resulting in a total of $210 in winnings.
