Diwali is actually Deepavali - the array of lights.
Diayas and lamps are an integral part of the festival
Walking down a street on Diwali night can be challenge thanks to the firecrackers, and also a pleasure as lights lined up against window sills and balcony parapets in the dark night make it look beautiful.
One of the main attractions of this festival are lamps that one lights and decorates the house with. It derives its name from the array of lights - deepam, avali.
The light signifies the end of darkness. It is believed that Rama returned to Ayodhya this day and that the people lit their homes that evening to reflect their happiness through the glowing lamps.
It is alos believed that Narakasura was killed that night or next morning and the lights signify the end of sorrow and the beginning of a new, bright dawn.