Definition - What does Tilak mean?
Tilak is a mark typically worn on the forehead by Hindus. It is a protective mark as well as a sign that shows religious affiliation.
There are different types of tilak in different sects of Hinduism. In the Vaishnava tradition, the tilak is called urdhva pundra and is usually made of sandalwood paste, clay or vermilion and applied as two lines that form a "U" shape, with a third vertical line in the middle. Saivites usually use a sacred ash, called vibhuti, and apply the tilak as three horizontal lines on the forehead, with a red dot at the center. This tilak is called tripundra. The devotees of Shakti and Devi use red turmeric powder, called kumkum, and draw only one vertical line or dot.
Yogapedia explains Tilak
The tilak is usually worn in the space between the eyebrows to mark the spot of the ajna (third eye) chakra.
There are three lines of a tilak and each represent various sacred trinities, such as the three sacred fires; the three syllables of the mantra, Aum; the three gunas; the three worlds; or the three gods, Brahma, Vishnu and Shiva.
Saivites believe that the three lines symbolize the three powers of Shiva: knowledge, will and action. In Vaishnavism, it is believed that the three vertical lines remind the wearer of the three gods, the three Vedic texts or the three realities.
Occasionally a tilak may be worn on other parts of the body parts such as the shoulders, chest or neck. It can be worn daily or for specific sacred rites and special occasions, depending on the local tradition.