Usually ‘Kumkum’ or sandalwood tilaks are applied during pujas. Commonly, a tilak is applied on the forehead, right between the two eyebrows with the ring finger. Both males and females do tilak where as married women are supposed to follow the tradition to always wear a tilak/kumkum on their forehead.

Now, the area right below the ring finger is known as the ‘surya parvat’ or ‘surya shetra’ while the ‘agaya chakra’ is situated on the forehead. By applying Tilak, a certain pressure point is pressed which gives a surya’ or sun like glow to the face.

Mind you, it is not just about aesthetics but the Tilak awakens the  ‘agaya chakra,’ from where an individual attains wisdom and fame.

In addition, the spot where Tilak is applied is home to a major nerve point in the complex human body.
This helps in retaining energy in our bodies which in turn helps in keeping one’s attention focused in one place.
Therefore, when tilak/kumkum is applied, we are also doing a ‘pooja’ in a way. [source]