Aegisthus had an affair with Clytemnestra, and they both killed Agamemnon - Clytemnestra's husband - during a banquet. Agamemnon is the commander-in-chief of the Greek forces when they invaded Troy. Orestes is the son of Agamemnon who sought revenge by killing Aegisthus. Homer mentioned the story a lot of times in order to provide a series of happenings regarding Oddyseus and his family after Agamemnon was slain.
