The Vedas meaning "knowledge" is derived from the root vid- "to know". They are a large body of texts originating in ancient India. Composed in Vedic Sanskrit (or some ancient languages), the texts constitute the oldest scriptures of Hinduism. The Vedic scriptures can be broadly classified into two categories: (1) The Shruti literature (heard or revealed) (2) The Smriti literature concerned with ‘the remembered.’.
Transmission of texts in the Vedic period was by oral tradition alone. But preserved with precision with the help of elaborate mnemonic techniques. A literary tradition was set in only during the Maurya period. The early Vedic tradition is consequently called shruti, "what is heard."
The Samhitas are hymns praising various Vedic Deities, which are Agni, Indra, Varuna, Mitra, Soma, the Rudras, the Vasus, and a whole host of Deities. These Deities are primarily "nature" Gods. These hymns formed the substance of the rituals used to propitiate these Deities.
Brahmanas are works detailing these rituals such as Agni Hotra or fire and other rituals. They elaborately describe the articles to be used as well as the procedures, significance and benefits of these rituals.
Four Shruti Vedas appear in early Sanskrit called Vedic Sanskrit. In addition to these four Vedas, there are a set of works collectively called the Vedangas, supplementary works dealing with grammar, meter, pronunciation, astronomy/astrology, and so forth.
The next branch of the Vedas are the Aranyakas, that takes the form in the Upanishads. Aranya means forest and aranyaka means "in the forest." The Upanishads are the premier theological discussions in the form of dialogues between students and teachers asking such question as, What is soul? What is God? What is the nature of reality? What is death? and so forth. The number of Upanishads varies with the highest number being over a hundred. Today, the most popular number of Upanishads may be 10 to 13.
Hinduism views time in great cyclic periods known as yugas. There are four such yugas and today we live in the time period known as Kali Yuga. Puranas are collections of ancient stories. The word purana means old and so they are compilations of old stories about gods, sages, and kings, along with the genealogies of famous royal families. Tradition mentions eighteen Puranas, the most common of which are: the Bhagavata, the Vishnu, the Shiva, the Skanda and the Garuda Puranas. There is even a set of smaller Puranas known as upapuranas that are also eighteen in number.
Like Vedas, Agamas and Tantras are a vast collection of knowledge and have come down through Guru-Sishya parampara, in oral traditions. The word Agama means 'that which has come to (us)'. Tantra means 'that which protects with detail'. Sruti, the eternal word, is said to be of two forms – Nigama (Veda) and Agama.
One can observe that the ancient Indian, Zoroastrian, Greek, Roman, and other religions all share a common heritage.
Zoroasters are people from iran, fire worshippers like the hindus. The Gods in Hindu mythology were called Devas, and the Villians were called Asuras. Now in Zoroaster mythology, the Gods are called Ahuras and the Demons are called Daevas. The Hindus call the mighty river of the Vedas the Saraswati and the Zoroasters call it the Harasvati. The Zoroasters called the Sindhu as Hindu, and that is how the people of the Sindhu valley were named. And the Iranian texts also claim to be as old as the Vedas. The Asur Mahadev of the hindu myth resembles the Ahura Mazda of the Iranians.
It appears that the Sapta Sindhu region or the Sarasvati region was the centre of this cultural tradition and origin of the Vedic texts. Arya means only a man from a Noble Family. Geologists say that the Sarasvati river dried up around 1900 BC. Since Sarasvati is the greatest river of the Rigvedic hymns, Rigveda may have been composed prior to 1900 BC.
Scriptures would have been originally developed (written/told) in many languages. The ancient India had very many language families and majority of them are extinct now. The Prakrits became literary languages, generally patronized by kings. The earliest inscriptions in Prakrit are those of Asoka. The various Prakrit languages are associated with different patron dynasties, with different religions and different literary traditions. The earliest records in Old Tamil are short inscriptions from around the 2nd century BCE in caves and on pottery. These inscriptions are written in a variant of the Brahmi script called Tamil Brahmi and the earliest long text in Old Tamil is the Tolkappiyam, an early work on Tamil grammar and poetics, around 1st century BC.
These are works on medicine, Ayurveda; law, the Dharma Shastra; architecture, Vastu Shastra; political science, Artha Shastra; morality, Niti Shastra; and of course, love and pleasure, the Kama Shastra. So all of these, the Shruti and Smriti Vedas, comprise the shastra or sacred writings of Hinduism.
There are also many other works that are not written in Sanskrit, like "Hindi Ramayana" known as the Ramcharit Manas, by Tulsi Das. The famous Hanuman Chalisa, forty verses in praise of Hanuman, is taken from this Hindi Ramayana. Another set of books that are not in Sanskrit, in South India are 12 siva puranas by saivite saints and the works of the vaishanavite Alwars called the Divya Prabhanda. They are collections of beautiful devotional and theological prayers written in Tamil.