"The mekhitza is a divider between men and women in a synagogue. Sometimes it is simply a physical separation between the two sexes, such as a room divider or curtain. Sometimes the women's section is in a balcony."
"The reason for a mekhitza is to provide the men with a greater opportunity to focus on their prayers, rather than on the attractive women in the room."
"The women's section is stereotypically a place where women talk without regard for the prayer service." (from JewishVirtualLibrary.org)