Team Strength and matchup bars are displayed to help provide a comparison between teams, and to suggest which team is more likely to win. The higher your Team Strength is versus an opponent’s Strength, the more likely you are to win. 

 

But please note that a higher Team Strength does not guarantee a win, and poor results are possible even when you outrank someone (just like it's possible for a last place team to beat a 1st place team in MLB). Over time, it's likely that you'll have a winning percentage against teams you outrank.