After the above-mentioned sutras, we now come to the Vedanta-sutras. When it comes to Vedanta, many commentaries on it revolve around the Brahman. The Brahman generally means the all-pervading, self-existent power. The word brahman is based on the root word brah, which means vastness, power or expansion. It also denotes the Supreme Being, as well as the atman, the living being, who, when freed from the body, becomes situated on the level of Brahman, or the spiritual nature. The concept of the Brahman was, for the most part, first elaborated in the Upanishads. Therein we begin to find descriptions from which our understanding of it grows. It is described as invisible, ungraspable, eternal, without qualities, and the imperishable source of all things. (Mundaka Upanishad 1.1.6-7)
It is explained that Shankara’s advaita doctrine was based on the famous passage in the Chandogya Upanishad (6.10.3), tat tvam asi, meaning “That thou art.” He taught that “thou and that” were not to be regarded as object and subject, but as identical, without difference (a-bheda), like the real self (atman). Thus, anything that was variable, like the body, mind, intellect, and ego are objects of knowledge and not the atman.
These concepts were more fully explained on the basis of the Vedanta-sutras. The Vedanta-sutras are a systemization of sutras or codes for understanding Vedic knowledge. As you know, they are short codes that are later to be explained by the spiritual master, guru or spiritual authority. By themselves, without further explanations, it is not easy to fathom their depths. So it is these commentaries that contain the additional information about such things as the Brahman.
Vedanta means the conclusion of the Veda or end of all knowledge. Vedanta is also known as Uttara Mimamsa, or later examination, and is a companion to the Purva Mimamsa, or preliminary examination. The Purva Mimamsa deals with the early portions of the Vedas and the Uttara Mimamsa deals with the latter portions. The Vedic tradition, unlike other religions and philosophies, is rooted in such remote antiquity that its origin cannot be fully traced. The Vedic literature explains that it exists in the form of eternal spiritual vibrations and is present both within and outside the universal creation.