What is the virtue of the hijab for women, and what is the difference between a woman who wears the hijab and one who does not?

The hijab is a divine obligation and a symbol of chastity and modesty. Whoever observes it has accepted Allah's decree. As for she who abandons it and displays herself immodestly, she deserves severe punishment. The Prophet, peace and blessings be upon him, described in an authentic hadith those women who are "clothed yet naked" as those who will not enter Paradise nor smell its fragrance.