What is character motivation?

a character’s ultimate desire or goal
the struggle between forces in the plot
the force that brings conflict to the protagonist
careful and deliberate word choice in writing

It would be "a character's ultimate desire or goal."
character motivation can be described as the reason why the character is acting this way. It can also be described as the reason why the character is motivated to do what he/she is doing in the plot. 

The main themes of the play are: fate and free will with the inevitability of oracular predictions is a theme that often occurs in greek tragedies the conflict between the individual and the state similar to that in sophocles’ “antigone” and   people’s willingness to ignore painful truths both oedipus and jocasta clutch at unlikely details in order to avoiding facing up to the inceasingly apparent truth and sight and blindness the irony that the blind seer tiresius can actually “see” more clearly than the supposedly clear-eyed oedipus, who is in reality blind to the truth about his origins and his inadvertent crimes.