Happy Diwali to all of the Hindi faith! This is a festival of lights that many of the faith celebrate because it represents the victory of light/good over darkness/evil in a spiritual sense. The day before major renovations cleaning and decorations are done to further symbolize the holiday’s meaning.
The whole holiday season has a combination of days such as Dhanteras, with Diwali in the middle and Bhai Dooj at the end. Believed to be started after 500 AD and associated with Lakshmi (the goddess of wealth and prosperity) the Hindi holiday has a history deep in history and positivity giving the faithful hope and in certain parts of India it is the start of the new Hindi year.
Mind you that the United States finally recognized this holiday back in 2003 when Dubya officially celebrated it at the White House with official status in 2007! This holiday also is related to psychology in the terms of being focused upon self-improvement, and self-inquiry, the basis is to be better, focus upon the positive within and to spread that positivity to others.
This is usually done through giving food (sweets, dry fruits, and seasonal specialties) to family, gift giving (this time is a huge shopping season like Christmas) and lighting fireworks, just like the 4th of July to physically show their commitment to Diwali.
I found an article that explains how many here in America and so forth are trying to use this holiday as an opportunity to explain the faith and the holiday. As it is very similar to Christmas with the message of rebirth, victory over darkness, decoration and the giving of gifts, I believe the holiday should be easy to explain to the American public.
And here is the official website: