In plain words
These are called the Āraṇyakas precisely because the man who had taken up the vānaprastha āśrama entered the forest and used this mantra as he meditated on God and contemplated God. Then, as for the Sāma. It has taken on a form of its own. If man is to spend his life always in joy, in zest and in delight, it is the chief sūtra of music, music made of certain kinds of feeling, melody and rhythm. The Sāma is the true essence of every kind of music. So Veda Vyāsa set it apart and went on fitting its inner essence into all the Vedas.
All these Vedas: they went on bringing this into the four āśramas ordained for men alone. To all four āśramas, brahmacarya, gṛhastha, vānaprastha and sannyāsa, this Veda has taught the same divinity. Not only that: for the fourfold puruṣārthas too these have stood as their most important embodiments of meaning. Dharma, artha and kāma, all three of these are essential for man in life. But to enjoy them in due order and on the right path, to practise them and to show them forth as an ideal, the Vedas have stood as the authority. Every action of the man of Bhārata: following this Veda alone, following the meaning of the Veda alone, the meaning of life has become fixed.
Anantovai vedāḥ. Though the Vedas are infinite, they set up three Vedas alone on the principal level for the welfare of mankind. The Veda means that which reveals the principle of Brahman. Vedeśirobrahma. The whole world is pervaded by Brahman alone. It is of the nature of sound. It spreads forth with eight kinds of names. That is:
Śabdabrahmamayi carācaramayi jyotirmayi vājmayi nityānandamayi parātparamayi māyāmayi śrīmayi
In ways like these, this divine essence of the Veda has spread forth along so many paths for the welfare of mankind. But all these Vedas have taken shape only under the avidyās. That is, these were suited only to worldly life; this gave no encouragement at all to go forward towards the principle that is beyond the world.