Dasara is celebrated allover India with a lot of fanfare and religious fervor. A religious as well as a social festival, Dasara is an occasion for pujas and festivities like music, dance and cultural programmes. In Southern India, especially in TamilNadu, Dasara is celebrated as Navarathiri.
Navarathiri means nine nights.

Mythology
According to Hindu mythology, a very powerful Asura-demon king Mahishasuran prayed to the almighty and asked for a boon - that his death should at the hands of a woman and by no other human being or any form of living being.
On being granted his wish, he started inflicting atrocities on all human beings on the earth. He considered himself to be immortal as he thought that it was impossible for a woman or any female form of a human being to be powerful enough to kill him.
When his cruelty became unbearable, people prayed to Sakthi the consort of Lord Shiva to save them from the demon and to provide them with salvation. Sakthi then took the form of Durga and slayed the demon.

Ayigiri Nandhini Nandhitha Medhini
Viswa Vinodhini Nandhanuthe
Girivara Vindhya Sirodhini Vasini
Vishnu Vilasini Jishnunuthe
Baghavathy He Sithi Kanda Kudumbhini
Boori Kudumbhini Boorikruthe
Jaya Jaya He Mahishasura Mardhini
Ramyaka Bardhini Sailasuthe.