Vedas are large bodies of literature considered to be foundational to the evolution of Hindu thought. It is believed that the Vedas were not written but heard by ancient sages (rishis). It is for this reason that they are sometimes referred to as shruti – ‘that which was heard’.
There are four primary Vedas – Rig, Sama, Yajur and Atharva Veda.
Each Veda is sub-divided into four parts (note that Atharva Veda does not have an Aranyaka section):
(1) Samhitas – hymns in praise of various vedic gods like Agni (the god of Fire), Varuna (the god of the oceans), Indra (the god of thunder, storms and rain) , Soma (personification of a beverage that was a prominent ritual offering) etc.
(2) Brahmanas – elaborate discussions around the performance of fire rituals (yajña or havan)
(3) Aranyakas – discussions about mystical and symbolic meaning of various Vedic rituals
(4) Upanishads – discussions about philosophy and nature of existence
It may be noted that some scholars use the term “Veda” to refer to only the samhita portion of the Vedas, as they believe that the Upanishads were composed separately and added to the Vedas at a much later date. Hindus, however, tend to use the term more broadly to include both the ritual part (karma-kanda) and the knowledge part (jñāna-kanda) of the Vedas.