Symbolism, Imagery, Allegory
One perspective of Electra is that the play is a moral one. Sophocles is interested in the different viewpoints of a morally sticky topic: vengeance. We can see each character as a different prism through which we examine this theme. Electra is staunchly idealistic; Chrysothemis is firmly pragmatic; Orestes is resolutely determined.
The debates between the two sisters, in particular, can be seen as representative of a larger dialectic going on in the play. This moral debate is one aspect of Sophocles's Electra that makes it stand out from the plays of Aeschylus and Euripides. In fact, this kind of debate and the larger issue of morality are noticeably absent from other Greek tragedies, and lend a more modern feel to the play.