What are the Vedas? They are no mere holy books in Hinduism, but eternal, without a beginning or an end, spiritual laws discovered by rishis. Swami Vivekananda says that they are ‘the accumulated treasury of spiritual laws.’
Veda means the sum total of eternal truths; the Vedic Rishis experienced those truths; they can be experienced only by seers of the supersensuous … That is why in the Vedas the term Rishi means ‘the seer of the truth of the Mantras’, and not any Brahmin with the holy thread hanging down the neck. The division of society into castes came about later on.
Veda is of the nature of Shabda or of idea. It is but the sum total of ideas. Shabda, according to the old Vedic meaning of the term, is the subtle idea, which reveals itself by taking the gross form later on. So owing to the dissolution of the creation the subtle seeds of the future creation become involved in the Veda.
All the created objects began to take concrete shape out of the Shabdas or ideas in the Veda. For in Shabda or idea, all gross objects have their subtle forms … the Shabda-state of every object is its subtle state, and the things we see, hear, touch, or perceive in any manner are the gross manifestations of entities in the subtle or Shabda state. Just as we may speak of the effect and its cause. Even when the whole creation is annihilated, the Shabda, as the consciousness of the universe or the subtle reality of all concrete things, exists in Brahman as the cause. At the point of creative manifestation, this sum total of causal entities vibrates into activity, as it were, and as being the sonant, material substance of it all, the eternal, primal sound of ‘Om’ continues to come out of itself. And then from the causal totality comes out first the subtle image or Shabda-form of each particular thing and then its gross manifestation. Now that causal Shabda, or word-consciousness, is Brahman, and it is the Veda. This is the purport of Sayana.
Source - Complete Works Of Swami Vivekananda 6.496–8.