Why do we light Vizhakku (Lamp)

Aum Namah Shivaya

Hinduism is not a religion but a way of Life. Unlike other religions, Hindu Dharma has many specialities. This is not known as a religion, it is known as the Dharma, Sanaathana Dharma. According to Bhagavath Geeta, Sanaathana means which cannot be destroyed by Fire, Weapons, Water, Air, and which is present in all living and non-living being. Dharma means, the way of life which is the "Total of all aachaaraas or customs and rituals."

In almost every Indian home lamp / Villakku is lit daily before the Altar of the Lord. In some house it is maintained continuously - Akhanda Deepam. All auspicious function commence with the lighting of the Villakku, which is often maintained throughout the function.

Light symbolizes Knowledge and Darkness - Ignorance. The Lord is the "Knowledge Principle" who is the source, the enlivener (An agent that gives or restores life ) and the illuminator of all knowledge. Hence Light is worshipped as the Lord himself.

Knowledge removes ignorance just as light removes darkness. Also knowledge is a lasting inner wealth by which all our acievement can be accomplished.Hence we light the lamp to bow down to knwlodge as the greatest of all forms of wealth.

The Lamp has further spirutual significance. The Oil or ghee in the lamp symbolises our Vaasanas or negative tendencies and the wick (Thiri) symbolises ego, When lit by spirutual knowledge, the Vaasanas get slowly exhausted and the ego too finally perishes. The flame of a lamp always burns upwards, similarly we should acquire such knowledge as to take us towards higher ideals.
Whilst lighting the lamp we thus pray :

Deepajyothi parabrahma
Deepa sarva tamopahaha
Deepena saadhyate saram
Sandhyaa deepo namostute

Meaning of the Slokam : I prostrate to the dawn / dusk lamp, whose light is the knowledge principle (the supreme lord) , which removes the darkness of ignorance and by which all can be achieved in life.
The following points to be noted while Lighting lamps :

The lamp can be lit by Ghee or oil . Sesame oil / Gingely oil destroys all evils. lighting with castor oil brings joy to the relatives. We should not use Groundnut Oil.
Neem oil, Ghee, Iluppai( A tree name..In English it is called as Mahua ) oil gives wealth. For Kula Deivam - Ghee, Castoroil, Neemoil, Coconutoil, Iluppaioil. For Goddess Mahalakshmi--ghee. Lord Ganesha--coconut oil. Lord Narayana--sesame oil

The Cotton wick (Thiri) is best as it would give Prosperity. And wick made out of New Yellow cloth gives Devi's blessings.

The Lamp lit towards the east removes Sorrow and Evil , West removes Debt , Enemies.

Always use two wicks for lighting the Lamp.

After lighting the lamp dont rub the excess oil on your hair; (it will make you loose your wealth) general beleif. Also rubbing in your own dress is also not good.So keep a piece of cloth in your pooja room and rub the excess oil in it .

Never keep any lamp directly on the kolam. Always keep it on a plate ( can be brass, silver not steel).
If you like keep a few grains of raw rice below the lamp - this is necessary only when you do vilakku poojai etc & not necessary everyday.

As soon as you finish namaskarams, shlokas etc, it is customary to keep a dot of milk on either side of the burning lamp after which you can put it off. After it burns for a minimum 30 mts, you can put it off, there is nothing wrong.

After head bath, one should remove the head towel before even lighting the lamp .
Lemon (Elumichai) vilakku lighting should not be done at home at all. It is to be lit only in temples. There is no harm in lighting the usual villakku at rahu kalam & chanting Durga shlokams, particularly on tuesday & friday at home.