What is the relationship between hijab and modesty, and does modesty differ between men and women?

Shyness (Hayaa'), according to Islamic law, is avoiding what is ugly and not falling short in fulfilling rights. It prevents the one who possesses it from committing forbidden acts. Thus, shyness and hijab are intertwined for a woman. As for a man, he is not required to wear hijab. Therefore, legal shyness (Hayaa' Shar'i) becomes obligatory for a woman in certain situations, but not for a man.