Purana

Purana (पुराण) - Ancient Scriptures pertaining to Hinduism

The Puranas (Vishnu Puran, Shiv Puran and Brahma Puran) sing the glory of Brahm (Kaal). He is addressed as Mahavishnu in Vishnu Purana, Mahabrahma in Brahma Purana and Mahashiva (Sadashiv) in Shiva Purana. Mahavishnu, Mahabrahma or Mahashiva (Sadashiv) are the forms of God Kaal. Brahma Vishnu and Shiva are the children of this God Brahm.

Shrimad Devi Bhagwat Purana also gives us information about Mother of Lord Shiva, Vishnu and Brahma

All the Puranas were compiled by Sage Ved Vyasa. 

Origin of Puranas

Brahma was the first recipient of Vedas after the churning of the great ocean. Brahma read the vedas and gave the knowledge to his descendants. Descendants of Brahma are various rishis (sages). The tales and stories told by Brahma after reading the vedas to his descendants formulated the content of the Puranas.

This is the reason Puranas are below the Vedas and the Bhagavad Gita in the hierarchy of holy scriptures pertaining to Hinduism with the vedas being at the summit. As Bhagavad Gita is considered the summary of the four vedas, it comes next to the vedas in hierarchy.