The oldest literature of Indian thought is the Veda, a collection of religious and philisophical poems and hymns composed over several generations beginning as early as 3000 BC. The Veda was composed in Sanskrit, the intellectual language of both ancient and classical Indian civilizations. Four collections were made, so it is said that there are four Vedas. The four as a group came to be viewed as sacred in Hinduism. Some Vedic hymns and poems address philosophic themes, such as the henotheism that is key to much Hindu theology. Henotheism is the idea that one God takes many different forms, and that although individuals may worship several different gods and goddesses, they really revere but one Supreme Being.
There are four Vedas:
Its traditional date goes back to 3000 BC, something which the German scholar Max Mueller accepted. As a body of writing, the Rig-Veda (the wisdom of verses) is nothing short of remarkable. It contains 1028 hymns (10,589 verses which are divided into ten mandalas or book-sections) dedicated to thirty-three different gods. The most often addressed gods were nature gods like Indra (rain god; king of heavens), Agni (fire god), Rudra (storm god; the ‘howler’), Soma (the draught of immortality, an alcoholic brew).
The Sama-Veda or the wisdom of chants is basically a collection of samans or chants, derived from the eighth and ninth books of the Rig-Veda. These were meant for the priests who officiated at the rituals of the soma ceremonies. There are painstaking instructions in Sama-Veda about how particular hymns must be sung; to put great emphasis upon sounds of the words of the mantras and the effect they could have on the environment and the person who pronounced them.
The Yajur-Veda or the wisdom of sacrifices lays down various sacred invocations (yajurs) which were chanted by a particular sect of priests called adhvaryu. They performed the sacrificial rites. The Veda also outlines various chants which should be sung to pray and pay respects to the various instruments which are involved in the sacrifice.
The Atharva-Veda (the wisdom of the Atharvans) is called so because the families of the atharvan sect of the Brahmins have traditionally been credited with the composition of the Vedas. It is a compilation of hymns but lacks the awesome grandeur which makes the Rig-Veda such a breathtaking spiritual experience.