Upanishads: vedic knowledge

Upanishads are the essence of the knowledge what indian philosophy or vedic philosophy hands over to the generations for their upliftment and self realization. To know Thyself, you should atleast open and know what these upanishads are teaching. Each upanishad is a smaller one in text but profound in disemminating the knowledge. There were 108 upanishads ( some say more than 108). But 10 are very important and contain the essence of all the 108 upanishads.These are:
  Aitareya   , Brihadaranyaka ,   Chandogya,    Isa ,
  Katha ,   Kena  ,  Mandukya  ,  Mundaka   , Prasna ,
  Svetasvatara,    Taittiriya  
Upa means near, and nishat means sit. upanishad means sit very near and learn the esoteric brahma gyan. These are at the end of each veda. the knowledge expounded is very great and supreme. The knowledge is in the form of abstract. It would be a little bit difficult to gain the full meaning of the upanishad without a proper teacher. One can get the help of the commentaries written on these upanishads. on line one can have the entire text of upanishads from the url. http://www.bharatadesam.com/spiritual/upanishads/kena_upanishad.php
These are the transalation of upanishads by swami nikhilananda.
It is highly advisable to one who wants to know the supreme knowledge about the unseen god and his creation, to learn slowly about upanishads and ponder over their meaning for days and days. Great gurus provided wonderful commentaries and lectures on thse which would be very helpful . Upanishads are authoritative in declaring any truth and till now they are not questioned . When we read them we can understand how terse, pithy they are and how logical they derive the facts and truth.