What do people do to celebrate Diwali / Divali and why?

Ahaha, well it's on Wikipedia.... But, as a Hindu, I'd just like to say I think it's pretty awesome that you have this assignment. That said, Diwali is the five-day festival of lights that we celebrate in either October or November (Hindu-ism revolves around the lunar calendar). Basically, it commemorates Lord Ram, his wife, Sita, and his brother (or half-brother, but whatever), Lakshman, returning from their fourteen-year exile to their kingdom of Ayodhya.

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. While the story behind Deepavali and the manner of celebration varies from region to region (festive fireworks, worship, lights, sharing of sweets), the essence is the same – to rejoice in the Inner Light (Atman) or the underlying Reality of all things (Brahman).

A Decorate entrance door with nice colourful fresh Marigold flowers strings along side with ashoka leaves in between. B Put a beautiful & colourful rangoli in front of your main door. C Put out decorative lamps /diyas, Candles on the rangoli, D At the entrance in midst of rangoli you can place a big bowl of water and floating candles in them with petals of rose flowers. E Put twinkle lights /lanterns /kandils/Parekh Flag F At the pooja, lit up the scented agarvati which gave a divine aroma in the room.

sorry dunno