Hindu religious literature is the large body of traditional narratives related to Hinduism, notably as contained in Sanskrit literature, such as the Sanskrit epics and the Puranas. As such, it is a subset of Indian mythology.
The four Vedas, notably the hymns of the Rigveda, contained allusions to many themes (see Rigvedic deities, Rigvedic rivers).
In the period of Classical Sanskrit, much material is preserved in the Sanskrit epics, the Ramayana and the Mahabharata. Besides theology proper, the voluminous epics also provide a plethora of information about ancient Indian society, philosophy, culture, religion and ways of life.
The Puranas deal with stories that are older than the epics (Purana is Sanskrit for "ancient"). The date of the Puranic texts as preserved however mostly post-dates the epics, dating to the Early Middle Ages.
The epics themselves are set in different Yugas (epochs) or periods of time. The Ramayana, written by the poet Valmiki, describes the life and times of Lord Rama (the seventh avatar of Lord Vishnu) and occurs in the treta yuga, while the Mahabharatha that describes the life and times of the Pandavas, occurs in the Dwapara yuga, a period associated with Lord Krishna (the eighth avatar of Lord Vishnu). In total, there are 4 Yugas. These are the Satya Yuga (or Krita Yuga), the Treta Yuga, the Dvapara Yuga and finally the Kali Yuga.
The Bhagavata Purana is probably the most read and popular of the puranas. It chronicles the story of the god Vishnu and his incarnations (avataars) on earth.
The roots of theology that evolved from classical Hinduism come from the times of the Vedic civilization, from the ancient Vedic religion.
The characters, theology, philosophy and stories that make up ancient Vedic myths are indelibly linked with Hindu beliefs. The Vedas are said to be four in number, namely RigVeda, YajurVeda, SamaVeda, and the AtharvaVeda. Some of these texts mention mythological concepts and machines very much similar to modern day scientific theories and machines.
The two great Hindu Epics, the Ramayana and the Mahabharata tell the story of two specific incarnations of Vishnu (Rama and Krishna). These two works are known as Itihasa. The epics Mahabharata and Ramayana serve as both religious scriptures and a rich source of philosophy and morality for a Hindu. The epics are divided into chapters and contain various short stories and moral situations, where the character takes a certain course of action in accordance with Hindu laws and codes of righteousness. The most famous of these chapters is the Bhagavad Gita (Sanskrit: The Lord's Song) in the Mahabharata, in which Lord Krishna explains the concepts of duty and righteousness to the hero Arjuna before the climactic battle. These stories are deeply embedded in Hindu philosophy and serve as parables and sources of devotion for Hindus. The Mahabharata is the world's longest epic in verse, running to more than 30,000 lines.