One of the unique features of a traditional synagogue is that men and women are separated for all prayers. In many older synagogues, women sat in a balcony above the main synagogue. In many synagogues today, there is a partition (mechitzah) separating the men and women. 

When did we start separating men and women in the synagogue? What is the reason for it? 

A fascinating discussion about separating  men and women in the synagogue