The Upanishads constitute the end part of the four Vedas namely the Rigveda, Yajurveda, Samaveda and Atharvaveda. Hence, they are also known as Vedanta, meaning the end of the Vedas (Veda + Anta). They represent the highest thought of the Vedic religion, and so also Hinduism.
The Vedanta school of philosophy is derived mainly from the knowledge of the Upanishads only. It has many branches such as the Dvaita, Advaita, Vishishtadvaita, Dvaita Advaita and so on. All these schools acknowledge Brahman as the highest supreme reality and the whole creation as his manifestation, emanation or projection, representing the alternate reality or the illusion (Maya). Understanding Brahman and our relationship with him is crucial to spiritualize our lives and achieve liberation by practicing Dharma and exemplifying God’s eternal duties upon earth.
The meaning of the word Upanishad
Two possible, traditional meanings have been ascribed to the word Upanishad. According to the first, Upanishad (upa+ni+sad) means sitting near or down. It refers to the way the Upanishads were taught to the students in ancient India. The knowledge of the Upanishads was confined to a few teachers who were either Kshatriyas or Brahmanas. They directly passed on the knowledge in person to a few select students according to their merit and under an oath of secrecy.
Since the knowledge was taught to students who sat near the master, at a lower level or at his feet, while the master sat on a higher seat (asana), his teaching was called Upanishad. Since secrecy was associated with the teachings, the knowledge of the Upanishads is also known as the secret knowledge (gudha) or utmost secret knowledge (athi gudha).
According to the second interpretation Upanishad means the knowledge which destroys the bonds of ignorance and leads to liberation. The knowledge of the Upanishads is essentially the knowledge of Supreme Self (Brahman) and the individual Self (Atman). Knowledge of these two eternal realities is considered true knowledge or pure knowledge (sat), in contrast to the worldly knowledge (asat) which is temporary and which leads to ignorance, delusion and bondage to the cycle of births and deaths. Since the knowledge of the Upanishads destroys ignorance, it is considered liberating knowledge. In his commentary on the Taittiriya Upanishads, Sri Shankaracharya suggested that Upanishad meant that which led to the highest bliss. What he probably meant was that the knowledge of the Upanishads would lead to eternal bliss by destroying bondage and suffering.
A third interpretation is also possible which leads to the same meaning. Upa, which is usually used as prefix to a verb or a noun has several meanings. It means an advice or the instruction of a teacher, reverence or worship and nearness or proximity in space, number, time or degree. Traditional interpretations of the Upanishad take the last meaning into consideration. If we go by the other meanings, Upanishads means an instruction or advice by a teacher in close proximity from a higher ground of awareness (upa) to students sitting below (ni) regarding the destruction (shad) of ignorance, bondage, etc.