The Upanishads are a collection of sacred texts that form one of the foundations of Hindu religious thought. The most important of these texts, written between about 600 and 300 B.C. , deal primarily with the nature of humans and the universe. Originally passed on orally, these works were eventually collected and written down by wise men called rishis.
The texts of the Upanishads are said to hold the "hidden meanings" of the religious practices and ideas presented in the Vedas, an older collection of sacred texts. Hindu beliefs based on the Upanishads are known as the Vedanta, which means that they came after the Vedas.
Rather than focusing on religious ritual and practice, the Upanishads are philosophical works that explore the nature of reality and meaning of life. One of their central teachings is the idea that behind the everyday world is a timeless, unchanging reality or spirit, called brahman, that is identical to the inner essence, or atman, of the human being. Unity with brahman and knowledge of the hidden reality behind existence can be achieved through yoga, which involves philosophical investigation and the highly disciplined practice of meditation.
ritual ceremony that follows a set pattern
The Upanishads also present the Hindu idea of reincarnation, in which individuals are reborn again and again as other living creatures. The main purpose of the Upanishads is to help individuals gain the mystical knowledge that will release them from this continuing cycle of death and rebirth.