salient features of aristotle concept of tragedy

Aristotle's conception of tragedy is an imitation (Platonic mimesis) of "an action that is serious, complete, and of a certain magnitude; in language embellished with each kind of artistic ornament, the several kinds being found in separate parts of the play; in the form of action, not of narrative; with incidents arousing pity and fear, wherewith to accomplish its katharsis of such emotions."

This is a good place to start--although a thorough analysis of each separate term would be more conducive to a proper understanding.