A fundamental aspect of Jewish life is modesty. It's evident in the way we walk in the street, in the way we interact with others, and in the way we dress.
The exact parameters for modest dress requirements depend on the time and place. However, the basic idea, for both men and women, is to wear clothes that respect the person, that is, clothes that do not diminish the importance of the person behind them by emphasizing the body as if it were more important than the spiritual qualities and virtues that are the main elements of personality.
When we avoid focusing excessively on our outward appearance, our human core, the Divine spirit within us, can shine through. Modesty in dress allows us to interact with the world in a much more powerful way, because our true essence comes to the surface.
Modesty does not mean denying one's own being or forcing one to hide it, but rather creates a space of privacy in which we can develop without worrying about the approval of others.
Even in solitude, in the most private of places, we must behave with modesty, for there is no place where God is not present.
Some basic guidelines:
Clothes that are tight to the body or that leave normally covered parts of the body visible, or even clothes that attract too much attention, should be avoided.
Women wear skirts that cover down to the knees (even when seated) and clothes that cover down to the elbows.
Married women cover their hair. They may do so with a wig or a cap.