Can someone tell me how games behind his done. I know the basics,

Games behind? I'm taking a guess you mean score wise?

Example-

The Red Sox are in first place. The Yankees are in second. If the number under "GB" for the Yanks is 4, that means the Yankees are 4 games behind for first place. If the Orioles are in third place, and the number under "GB" for them is say, 7, that means the Orioles are 7 games behind the Red Sox.