The Prologue is all that precedes the Parode of the chorus; an Episode all that comes in between two whole choral songs; the Exode all that follows after the last choral song.
The prolusion needs to be designed well, a exquisite and claptrap prolusion can grasp the attention of the audienc immediately and it lays a good foundation for a successful demostration.
The first one is what I call the strong first line, is whenever you're gonna speak English or be in a situation where you speak English, have your first line ready.