At the end of each Veda is a section called the Upanishad which literally means, "sitting close, with devotion." They were composed between 1300 and 800 BCE. Etymologically, the word suggests sitting at the feet of an illumined adept in an intimate session or spiritual instruction. This final section of each Veda contains the "secret teachings" of the ancients, which, over the centuries, have been well-guarded and meant for the most worthy disciples. The Upanishads inquire into the nature of reality, God, and the universe. They are more probing than the rest of the Vedas, and they address the essential issue of how a seeker can attain God-Realization. The Upanishads teach that the Absolute Reality, Brahman, dwells fully in the human soul; and that this Reality is meant to be known. The teachings of the Upanishads are called Vedanta, which means "at the end of the Vedas."
Source : Jonathan Star, The Inner Treasure