Theatre began as a ritual to worship Bacchus, drama and wine. There was a chorus that told stories and praised Bacchus, and danced, very orgiastic. Then Thespis (ie thespian) got drunk and got out of line (literally) and made the great leap: impersonating the character, speaking for them, not just talking about them. Ah, the insights of wine.
Now, because the chorus danced while they performed, their words had to be in rhythm (again, just like rap). The beats in each line were called feet because of this and had two parts, stressed and unstressed, like a foot hitting the floor. Also, because they were talking about gods and heroes (and were very drunk) they needed elevated language.
Given the ritual nature of it, theatre was IMPORTANT. It was performed once a year, for the festival, in Athens. The winning playwright was HUGE. Only citizens (no women) could attend.
Structure of the festival: Satyr play (satire), then tragic trilogy (Only surviving trilogy: The Orestia)
Big Four: Aeschylus (the first, 525-456), Sophocles (the greatest 496-406, 123 plays, seven survive), Euripides (the innovator, 484-406), Aristophanes (the comedian).
Tropes: Chorus. Audiences address. Technical specs for performance (masks, stilts, doors, deus ex machine, seating, orchestra). Invocation of the gods. Stories the audience knew (and watching how it unfolds, character vs. plot, irony). Tragic structure (peripetiea (unintended effect), anagnorisis (realization), catastrophe (pity and fear), catharsis (purging)) Messenger speeches (violence offstage, occasional reveals (the Furies and giving birth)).