Dasara is celebrated on the tenth day of Navaratri and is also called Vijayadashami. There are many legends associated with the celebrations on this day. One of the popular ones is that of Lord Rama Killing the Demon Ravana on this day. Lets see how this was done.
Lord Rama had to go on exile along with his wife Sita for many years. When he renounced his kingdom and decided to go on exile, his brother Lakshmana also decided to accompany him on the exile. When he was residing in the forests along with Sita, one day Ravana disguised himself as a Brahmin and kidnapped Sita and took her away to his hometown Lanka (which is now Sri Lanka).
Lord Rama along with his brother went about searching for Sita and headed towards Lanka. During their journey to Lanka, they were helped by Hanuman and his vanara sainya (army of monkeys). They built a bridge for him till Lanka. Then a fierce battle begun which went on for many days. Finally Lord Rama performed the Chandi Puja and prayed for the Goddess Shakti to help him in the battle. The Goddess Durga blessed Rama with the secret knowledge of the way to kill Ravana. On the final day of the battle, Rama succeeded in killing Ravana . This day came to be known as Vijaya Dashami.
People celebrate Vijaya Dashami on this day every year in order to commemorate the victory of good over evil. People gather in groups in temples and pandals and celebrate this occasion by worshipping Goddess Durga and celebrate the victory of Lord Rama.