The Chorus in "Oedipus Rex" serves several important functions in the play. The Chorus is composed of a group of elders from Thebes who observe what is happening and react to it as the audience is most likely to respond. The Chorus acts as the bystander who gets to ask the tough questions as well as the observer who explains things the audience does not know.
Because they are elders of the community, the members of the Chorus have been in the town for awhile and have experienced all the hardships. These elders, of course, know background information and other tidbits that they tell the audience. This information is hard to work into the play any other way. They act in some ways like a narrator telling parts of the story between character conversations. As a representative of society, the Chorus asks the questions to which the townspeople — and the audience — want answers. The group acts as the common people, the minor characters in the play, who are affected by all the bad things that are happening, and its members mirror those feelings for the audience to understand. At the same time, their emotions are the same as the emotions expected from the audience members, so the audience relates to the Chorus. Comprised of many, the group speaks and moves as one. Although its members are knowledgeable about a great deal of the plot, they represent humans and so are not perfect in their perceptions.