Ancient narration. The Puranas are, like the Mahabharata, composed by Vyasa. They are subdivided in 18 Mahapuranas, great Puranas, and 18 Upapuranas, secondary Puranas.
The 18 Mahapuranas: Agni, Bhavishya, Bhagavada, Brahma Vaivarta, Brahmanda, Garuda, Kurma, Linga, Markandeya, Matsya, Narada, Padma, Shiva, Skanda, Vamana, Varaha, Vayu, Vishnu. These Puranas have more than 400,000 verses.
The 18 Upapuranas: Sanatkumara, Narasimha, Brihannaradiya, Shivarahasya, Durvasa, Kapila, Vamana, Bhargava, Varuna, Kalika, Samba, Nandi, Surya, Parasara, Vasishtha, Devi, Ganesha, Hamsa.
Every Purana deals with five themes Panchalakshana.
See also Bhasha Traya
Puranas are to be found here