Good morning world!
Popularly known as the Festival of Lights or "the awareness of the inner light" (read more about that below), Diwali (also: Divali and Deepavali) is a very meaningful five day festival of Hinduism, Jainism and Sikhism. An official holiday in many countries, Diwali marks and celebrates the triumph of good over evil, the word Diwali derives from the word Deepavali which translates into "row of lamps," which is why Hindus, Jains and Sikhs light clay oil filled lamps throughout the five day festival to celebrate this triumph.
I really love the significance of this holiday, in fact there was so much stuff I wanted to paraphrase from Wikipedia that I just gave up, I want to post it all, so here goes...
This explains the specific significance of the holiday in each religion that celebrates it:
"Diwali commemorates the return of Lord Rama along with Sita and Lakshman from his fourteen year long exile and vanquishing the demon-king Ravana. In joyous celebration of the return of their king, the people of Ayodhya, the Capital of Rama, illuminated the kingdom with earthen diyas (oil lamps) and burst crackers. In Jainism, Diwali marks the attainment of moksha or nirvana by Mahavira in 527 BC. In Sikhism, Deepavali commemorates the return of Guru Har Gobind Ji to Amritsar after freeing 52 Hindu kings imprisoned in Fort Gwalior by defeating Emperor Jahangir; the people lit candles and diyas to celebrate his return." (via Wikipedia)
This explains the spiritual significance of the holiday, which I really love [read: bold text]:
"In each legend, myth and story of Deepawali lies the significance of the victory of good over evil; and it is with each Deepawali and the lights that illuminate our homes and hearts, that this simple truth finds new reason and hope. From darkness unto light — the light that empowers us to commit ourselves to good deeds, that which brings us closer to divinity. During Diwali, lights illuminate every corner of India and the scent of incense sticks hangs in the air, mingled with the sounds of fire-crackers, joy, togetherness and hope. Diwali is celebrated around the globe. Outside India, it is more than a Hindu festival, it's a celebration of South-Asian identities.While Deepavali is popularly known as the "festival of lights", the most significant spiritual meaning is "the awareness of the inner light". Central to Hindu philosophy is the assertion that there is something beyond the physical body and mind which is pure, infinite, and eternal, called the Atman. The celebration of Deepavali as the "victory of good over evil", refers to the light of higher knowledge dispelling all ignorance, the ignorance that masks one's true nature, not as the body, but as the unchanging, infinite, immanent and transcendent reality. With this awakening comes compassion and the awareness of the oneness of all things (higher knowledge). This brings Ananda (joy or peace). Just as we celebrate the birth of our physical being, Deepavali is the celebration of this Inner Light.
I really think every person in the world should celebrate the message of Diwali, regardless of their religion. Why? Because it's a very good message and something we must always remember within ourselves. Besides, the world could use more joy and peace. especially these days! The world needs more people to self reflect, to overcome ignorance and issues of race and religion in order to come together and attain true love, peace and happiness.
(All information about DIwali is from Wikipedia.org and images are via a Google image search)