A bindi is worn on one's forehead in between eyebrows and is a symbol of married women among Hindus, although with changing customs, it is used by unmarried girls also.
Earlier people used to apply kumkum and/or Chandan as a bindi or tilak. Bindis have a special significance even today. A red dot on the forehead is an auspicious sign of marriage and guarantees the social status of the guardian of the family thus ensuring the entire family's well being. The center where the bindi is put is the center of nerves named "Ajna chakra". This soothes the person and beats his anxiety.
It is also the position of the third eye. Widows in India do not wear bindi usually, but they are allowed to wear a black bindi. Young girls are free to wear any bindi.
Here are some benefits of wearing a Bindi
During meditation, the energy rises from the base of the spine towards the head. This point on the forehead is the outlet for that energy. The kumkum between eyebrows retain the energy in the human body. Woman also uses a circular disc or coin to draw a perfect bindi. First, they apply a sticky wax paste on their forehead. But today Bindi is made of glitter, stone etc and is only a fashion statement. This trend needs to be checked and use of bindi by Hindu women should be promoted for reaping it's myriad benefits.