Happy Diwali everyone! Known as the "Festival of Lights," Diwali is a celebration incorporating many faiths across India. Straight from Wikipedia:
"The name "Diwali" or "Divali" is a contraction of "Deepavali" (Sanskrit: दीपावली Dīpāvalī), which translates into "row of lamps". Diwali involves the lighting of small clay lamps (dīpa in Sanskrit: दीप) filled with oil to signify the triumph of good over evil. These lamps are kept on during the night and one's house is cleaned, both done in order to make the goddess Lakshmi feel welcome. Firecrackers are burst because it is believed that it drives away evil spirits. During Diwali, all the celebrants wear new clothes and share sweets and snacks with family members and friends."
In Hinduism, there are a variety of reasons to celebrate, based on where you live in India.
In Jainism, Diwali marks the celebration of Mahavir Bhagwan's attainment of nirvana in 527 B.C.E.
In Sikhism, the celebration of Diwali is celebrated because it rejoices the time when the sixth Sikh guru, Guru Hargobind singh was released from his imprisonment.
For whatever reason you celebrate, the end goal is to celebrate the triumph of good over evil. Oh, and to light a lot of candles, set off fireworks, eat tons of dessert, and spend some much needed QT with your family.