This is also the place where we focus for concentration during meditation and yoga. Many Indian saints have had records of having seen a bright light in the form of a Shiv Linga here. Thus this is viewed as a very sacred place. It is believed that all energies converge to this point in the body. This is called the main fulcrum of concentration.
The kumkum powder made of red turmeric is a coolant that helps to maintain the temperature here.
The sindoor is made out of zinc oxide and dye and is another form of kumkum.
In earlier days, in India, people used to apply tilak or a long kumkum on the forehead to protect the energies and strength within. It signifies surrender of ego to the Power above and of maintaining the strength within always.
Today with the advent of modern thinking, the bindis have become fashionable stickers and kumkum is passe in most women.
So the next time, you see an Indian Bindi, you know what it is all about. !