Diwali or Deepavali is a "Festival of lights"(deep = light and avali = a row i.e., Row of Lights). This festival comes exactly after 20 days from dussehra ends. And also in between mid-October and mid-November.
Apart from India, it is official holiday for country Like Nepal, Sri Lanka, Myanmar, Mauritius, Guyana, Trinidad & Tobago, Malaysia, Singapore and Fiji.
In Hindus, Deepavali is celebrated due to reasons like Marriage of Laxmi with Lord Vishnu and Return of Lord Rama along with Sita Mata and Lakshman from his fourteen year long exile and vanquishing of the demon Ravana, celebrated as Ramnavami/Dussehra. In Jainism, Diwali marks the attainment of moksha or nivana by mahavira in 527 BC.
One More reason to celebrate diwali is that, In Rural India it marked the End of harvest season, that means money from sale of produce which makes villagers to afford/buy new cloths and other things needed for the home.
Basically, its five days festival:
First Day of which called "Dhanteras", Dhan means Wealth and Teras means 13th day as per Hindu Calender. It is celebrated on the thirteenth lunar day of krishna paksha in Hindu calendar month of Ashwin.
On Dhanteras, Hindus consider it very fortunate to purchase gold or silver or at least one or more utensils as it believed that it is sign of Good Luck.
It is also Known as 'Yamadeepdaan' and the house ladies light eastern lamps or deep which kept burning throughout the night glorifing Yama, The GOD of Death.
Now, Second Day of which called "Naraka Chaurdasi" marks the vanquishing of the demon Naraka by Lord Krishna along with his wife Satyabhama.
(Diwali Image, diwali pictures)Third day is Amavasya, the day of Diwali/Deepavali which marks the workship of Lakshami mata, the Goddess of Wealth to fulfill the wishes of her devotees. On this day We lighten "Deep"(small oil lamps made of clay), or now a days with Electric light in House. It is also a symbol of removing darkness and spreading light in our life.
One More thing after doing pooja of Lakshmi mata and having so many sweets, is bursting crackers. This is the most important/enjoyable part for children’s, youths and also many middle age people enjoy doing.
One more scientific reason is that flames produces by crackers and deep kills a lot of insects and mosquitoes, found in plenty after the Rainy season.
Fourth day called as Chhota Diwali/Basiya Diwali, on this day also we lighten deep/Electric lights in small scale. It tells story of Lord Vishnu, who in his dwarf oncarnation vanquished the Bali, and banished him to Patala. And also This is ONLY day in a whole year when Bali is allowed to come on Earth to light millions of lamps to dispel the darkness and ignorance and spread the love and wisdom.
This is also marks the coronation of the Emperor "Vikramaditya" and so "Vikram-Samvat" was started, it is Hindu Calendar Starting in 57 BC.
Govardhan Puja is also performed in here on this day, as this day Godness Krishna lifted "Govardhan parvat(mounten)" to safe mathura people from angry Indra, who sent a deluge to submerge Gokul Because Lord Krishna prevented them from offering prayers to Indra and asked them to worship Govardhan Parvat(mounten).
In the last or Fifth day referred to as "Yama Dvitiya" or also called Bhai Dooj. On this occation Sisters do poojas for Long and Successful life for their brothers.
And that is how Diwali/Deepavali Ends Finally as a festival.
Let me ask one thing, since childhood we are celebrating diwali doing poojas, having sweets and many different Pakwan/Indian cuisine and bursting crackers But How many of us really applying the message which Diwali gives us? Its really not very important how this festival start, now it important what is the meaning of celebrating it in present?
Take for instance THE RAMAYAN, now a days we can not find brotherhood Like Rama-Lakshman, Rama-Bharat or we can't get anything like Bharat Milap. And also true story like Sharvan Kumar and his blind parents.
We need to come up from SELFISSNESS; Inner darkness that is what diwali festival tries to teach us every year. We need to respect our Elders. We need to choose correct path to move on instead of shortcuts or any wrong path and much more.
It teaches us to fight against all form of injustices, to fight against negativity, and most importantly fight for one's self-respect and dignity.
And in Last Happy, precious and Safe diwali this year.