The most well known story behind Diwali is in the Ramayana, the great Hindu epic. According to Ramayana, Rama, the prince of Ayodhya was ordered by his father, King Dasharatha, to go away from his country and come back after living in the forest for fourteen years. So Rama went on exile with his devoted wife Sita and faithful brother, Lakshmana. When Ravana, the demon king of Lanka abducted Sita and took her away to his island kingdom of Lanka, Rama fought against and killed Ravana. He rescued Sita and returned to Ayodhya after fourteen years. Hanuman, the monkey king and bears helped in this journey of finding Sita. To celebrate Rama’s return to Ayodhya, they lit up their houses with earthen lamps (diyas), burst crackers and decorated the entire city in the grandest manner.

This is believed to have started the tradition of Diwali. Year after year this homecoming of Lord Rama is commemorated on Diwali with lights, fireworks, bursting of crackers and merriment. The festival gets its name Deepawali, or Diwali, from the rows (avali) of lamps (deepa) that the people of Ayodhya lit to welcome their King.

Here is the link for the story:

May Goddess Lakshmi showers her blessings on your and your family..