[Spiritual Audiobook ] The Upanishads (1) 

The Upanishads are commonly referred to as Vedānta. Vedanta has been interpreted as the "last chapters, parts of the Veda" and alternatively as "object, the highest purpose of the Veda".The concepts of Brahman (ultimate reality) and Ātman (soul, self) are central ideas in all of the Upanishads, and "know that you are the Ātman" is their thematic focus.
The Sanskrit term Upaniṣad (from upa "by" and ni-ṣad "sit down") translates to "sitting down near", referring to the student sitting down near the teacher while receiving spiritual knowledge. Other dictionary meanings include "esoteric doctrine" and "secret doctrine".
Adi Shankaracharya explains in his commentary on the Kaṭha and Brihadaranyaka Upanishad that the word means Ātmavidyā, that is, "knowledge of the self", or Brahmavidyā "knowledge of Brahma".