In plain words
It is beyond all measure. It is full of Ānanda. This Veda was born from the root 'vida jñāne'. That is, Īśvara-jñāna itself is this Veda. Ātma-jñāna itself is the Veda. Brahma-jñāna itself is the Veda. Advaita-jñāna itself is the Veda. Vijñāna itself is the Veda. All of these are synonyms for Ātma-jñāna. But ordinary people cannot understand such a sacred Veda. Whether it is understood or not, the divinity of the Veda pervades everywhere. This is Śabda-brahman.
She who is Śabda-brahman, all that moves and moves not, light itself, speech itself, eternal Ānanda, beyond the highest, Māyā itself, Śrī Herself.
This itself is Brahman, full of Prajñāna. This itself is constant integrated awareness. It does not belong to one time or to one place. It belongs to the whole universe.
Knowing that it was not possible for ordinary people either to grasp such a Veda or to live by it, Vyāsa divided it into four parts. Though the Veda took four kinds of form, this whole Veda, made up of three kāṇḍas, has spread its message through the whole world in the form of practice. Karma-kāṇḍa, Jñāna-kāṇḍa, Upāsanā-kāṇḍa: in this threefold form is the Veda. Man is the master of karma. 'Karmaṇyevādhikāraste': he has taken on a body to have the right to action. We must perform these karmas so that they are full of Dharma. That is why we must recognise the truth that 'Śarīram ādyaṃ khalu dharmasādhanam': this body came into being for the practice of Dharma. When the karmas man performs come to ripeness, this itself turns into upāsana. When this upāsana is practised with the feeling of offering to God, in the divine principle full of Prema, it takes shape as full Jñāna. In short, karma, upāsana and Jñāna, all three, are one. Just as the fruit is born as a flower, turns into a green fruit and takes shape as the ripe fruit, so karma is like the flower. Upāsana is like the green fruit. Jñāna is like the ripe fruit. And so, that ordinary people might practise this form of karma, upāsana and Jñāna, the Purāṇas and Itihāsas too were created as its upāṅgas. The end of this Veda is the Upaniṣad. Because it is the end of the Veda, it is called Vedānta.