Esther became queen of Persia in 478 BC. Her true identity was a Jew.
Her given Hebrew name was Hadassah (which is derived from root word Hadass translated means Myrtle) Which name was kept hidden when she assumed the Persian name of Esther. Hadassah's history and family originated from amongst the Jews or Hebrews of the southern kingdom, those of the tribes of Judah and Benjamin 1 Kings 12:21.
These tribes had been conquered by the Babylonians under King Nebuchadnezzar and carried off in what is called the captivity. After the Babylonian empire was itself conquered and under Persian rule, the Jews and Benjamites were permitted to return to Jerusalem. Esther's family obviously did not make use of the permission granted by Cyrus for the exiles to return to Jerusalem. which sets the stage for the story.
Now king Xerse made a banquet where they drank and feasted many days. The king got angry at his current queen as the story goes, because she would not present herself at the kings command while he was entertaining his drunken friends. His advisers and all his friends got offended with the queens anti social behavior. As tradition has it she lost her position and head. Because it was not fitting that the king be queen-less; so his buddies got together and round up all the young maidens of the kingdom so that the king could find himself a new queen.
This is where Esther a young Jewess found herself in the round-up. When orphaned at a young age her parents having died some time ago and she was living with her cousin Mordacai who became like her father. Mordecai worked in the household of the Persian king Esther 2:5-7. It was Mordacai who brought her before the kings eunuch keeper of the king's harem. Who took one look at the girl and quickly gave her special cosmetics in preparation of one night with the king.
After being inducted into the kings harem and given maids to help prepare her for her possible one and only opportunity to become queen. She began a one year journey of beauty treatments and instructions for her shining debut that one night with a Persian king.
This would be a great challenge as we understand after entering the kings harem she would never have an opportunity to marry a young Jewish man raise children in normal fashion. She no longer had her own rights or will to choose. After this everything would be chosen for her. She chose to submit and give her all so that she would be seriouly considered for the position and truly prepare for her "one night with the king".