Meaning of 'Upanishad'
The term 'Upanishad' literally means, "sitting down near" or "sitting close to", and implies listening closely to the mystic doctrines of a guru or a spiritual teacher, who has cognized the fundamental truths of the universe. It points to a period in time when groups of pupils sat near the teacher and learned from him the secret teachings in the quietude of forest 'ashrams' or hermitages. In another sense of the term, 'Upanishad' means 'Brahma-knowledge' by which ignorance is annihilated.
The Upanishads form the core of Indian philosophy. They are an amazing collection of writings from original oral transmissions, which have been aptly described by Shri Aurobindo as "the supreme work of the Indian mind". It is here that we find all the fundamental teachings that are central to Hinduism — the concepts of 'karma' (action), 'samsara' (reincarnation), 'moksha' (nirvana), the 'atman' (soul), and the 'Brahman' (Absolute Almighty). They also set forth the prime Vedic doctrines of self-realization, yoga, and meditation. The Upanishads are summits of thought on mankind and the universe, designed to push human ideas to their very limit and beyond. They give us both spiritual vision and philosophical argument, and it is a strictly personal effort that one can reach the truth.