Almost every Indian household practices the ritual of lighting a lamp in the altar of the Lord. Symbolism is an important aspect of most Hindu rituals. The light symbolizes knowledge. In the traditional oil lamps like the one shown in this picture, the oil symbolizes our negative tendencies (ignorance, vice, etc.) and the wick, our ego. So the symbolic significance of lighting the lamp is to remind us that by lighting our minds with the fire of knowledge, we will exhaust our innate negative tendencies and our ego too, will eventually perish.