In the prologue of Sophocles' Oedipus the King, the title character emerges from the royal palace to encounter a crowd of Theban citizens. The Priest tells Oedipus that Thebans of every age and societal station have gathered at the various altars of their city to pray for help against and deliverance from the plague. The priest says that some of these people are very young ("some fledglings barely strong enough to fly"; Ian Johnston translation) and some are quite old. One of the groups consists of the most noble young people in the city ("the pick of all our youth"). The Priest also tells Oedipus that there are other priests there besides him. The Priest also specifies that he is a priest of Zeus ("I’m priest of Zeus").
So, the Priest who addresses Oedipus in the Prologue is a representative of Zeus at Thebes (each different Greek city-state would have different priests for the different divinities). All the other people crowded around Oedipus' palace are Thebans of various ages and social positions.