Oedipus; What is the purpose of the Strophe and AntiStrophe?

This is a dramatic convention. Typically you find strophes and antistrophes in odes, drama and other choral poetry. The chorus dances across the stage in one direction while chanting the strophe, then they turn and dance in the other direction during the antistrophe. The third movement (or the final movement if there are multiple strophes) is the epode when they stand in center. Generally poets use strophe and antistrophe to signal changes in thought or topic. As a modern reader, you can use them to get an idea of the structure of the chorus's long speeches.