(5) There was a certain Jew in Shushan the castle, whose name was Mordecai the son of Jair the son of Shimei the son of Kish, a Benjamite, (6) who had been carried away from Jerusalem with the captives that had been carried away with Jeconiah king of Judah, whom Nebuchadnezzar the king of Babylon had carried away. (7) And he brought up Hadassah, that is, Esther, his uncle’s daughter; for she had neither father nor mother, and the maiden was of beautiful form and fair to look on; and when her father and mother were deceased, Mordecai took her for his own daughter. (8) So it came to pass, when the king’s commandment and his decree was published, and when many maidens were gathered together unto Shushan the castle, to the custody of Hegai, that Esther was taken into the king’s house, to the custody of Hegai, keeper of the women. (9) And the maiden pleased him, and she obtained kindness of him; and he speedily gave her her ointments, with her portions, and the seven maidens, who were meet to be given her out of the king’s house; and he advanced her and her maidens to the best place in the house of the women. (10) Esther had not made known her people nor her kindred; for Mordecai had charged her that she should not tell it.
Isaac Sender, The Commentators' Al Hanissim: Purim
Masquerading also alludes to the miracle of Purim, which was "masked" within the laws of nature...Even the name of the Megillah and its heroine, Esther, allude to what is "hidden" or "masked". The Gemara asks: 'Where is Esther's name alluded to in the Torah? And the answer given is that it is alluded to in the verse: "And I will surely hide My face." For this reason we wear masks to emphasize the symbolism of camouflage.
Sidnie White Crawford, Chair of Classics and Religious Studies, University of Nebraska-Lincoln
The purpose of the Book of Esther is to demonstrate to Jews living in exile that it is possible to achieve success in the country of one’s exile without giving up one’s identity as a Jew. In this, the Book of Esther is similar to books such as Daniel or Tobit, or, in fact, to the historical character Nehemiah. However, the Book of Esther is unique in two important respects. First, the protagonist of the book, and the one with whom the audience should identify, is a woman, Esther (Mordecai is, of course, the other leading character and finishes the story at a very high rank, but this is basically because of his relationship to, and through the efforts of, Esther). This choice of a female hero serves an important function in the story. Women were, in the world of the Persian diaspora, as in many other cultures, essentially powerless and marginalized members of society. Even if they belonged to the dominant culture, they could not simply reach out and grasp power, as a man could; whatever power they could obtain was earned through the manipulation of the public holders of power, men. In this sense the exiled Jew could identify with the woman: he or she too was essentially powerless and marginalized, and power could be obtained only through one’s wits and talents. But, as the actions of Esther demonstrate, this can be done. By astutely using her beauty, charm, and political intelligence, and by taking one well-placed risk, Esther saves her people, brings about the downfall of their enemy, and elevates her kinsman to the highest position in the kingdom. Esther becomes the model for the Jew living in exile.