Baseball betting odds are a little bit different than football or basketball odds because baseball is a money line sport. That means all you care about is winning the game, no point-spread is involved.
Let's look at the baseball betting odds and the options you have. Baseball betting odds posted at the sportsbook would look like this:
Los Angeles Dodgers Penny 7.5 over
San Diego Padres Peavy -165
In this baseball betting odds example if you liked the Padres you would risk $165 for every $100 you wanted to win on San Diego. If you liked the Dodgers you would risk $100 and win $145 if Los Angeles won. The $20 difference is the vigorish and referred to as a 20 cent line in baseball odds. The 7.5 over is the total amount of runs for the game. It is also a 20 cent line in baseball betting odds and in this case would have the over at -120 and the under at even money.
The run line is baseball odds in terms of the spread. Since the scores in baseball are so low, the spread is always -1.5 for the favorite and +1.5 for the underdog. For the most part, you can turn a baseball favorite on the baseball betting odds board into an underdog on the run line. This is a less risky option for many bettors and why you see run lines played with heavy favorites on the baseball betting odds board.
Another difference with baseball odds is the listed pitcher vs. action option. When you bet on a baseball game, you are getting the baseball betting odds on the game based on the listed pitchers. If the pitcher changes and you listed the starting pitchers then you have no action. If you did not specify pitchers then you get action on the side you chose at the adjusted baseball odds. For example, if in that previous example Peavy does not start and they go with some rookie it could turn the game into a pick in baseball betting odds. You might not want your money on the Padres in that situation so you list pitchers to make sure Peavy starts the game.
Many bettors always list pitchers in baseball betting odds while some others go with action. You should know that 95% of the time the listed pitchers start the game. It is very rare when pitchers are changed on the baseball betting odds board.