Good was an abstract concept that incorporated a set of religious, or moral ethics antithetical to Evil. Good was usually constructive, beneficial, and orderly. Good could be used to describe actions or individuals (even non-corporeal entities), as well as ideas.
The Excalbians were interested in learning about the difference between Good and Evil when they pitted Kirk, Spock, Surak and Abraham Lincoln against Genghis Khan, Colonel Phillip Green, Kahless and Zora. (TOS: "The Savage Curtain")