The Indian tradition believes in the concept of atman, an inner light of strength that resides in the individual soul. Just as each individual celebrates the birth of his physical being each year, Diwali celebrates the inner strength of the soul. One reason why the darkest night of the Krishna Paksh, (the month of the Diwali holiday) is lit with a row of lights outside each home is to remind individuals of their inner strength, one that can light up even the darkest night.
India is celebrating Diwali, a major holiday not only for Hindus, but for Sikhs, Buddhists and Jains, too. Check out this beautiful picture of Diwali light in the UK Telegraph.