Make no mistake, i’m only a student and this is what i understood so far.
To hang these in your tree of knowledge you may compare them with the Weda’s and find they are more psychological and philosophical. They are teachings by those that at a riper age, abstained from there home or village life and retreated in the forest (Oepanishads, ir. A.J. Blok, 1976). Oepanishads belong to the world of Ritual (see Spiritual Hierarchies). Some students dive in and wish to know all at once. You will lose perspective. Passed on solely by verbal teachings Oupanishads were considered secret teachings.You will, untrained, not understand a syllable of what is written. First you’ll learn about Pradjapati, the Lord of all Creatures.  Pradjapati is Brahma, predecessor of the coming cosmos after a Pralaya or period of cosmic sleep. The secret Doctrine will show you how Brahma is then divided is two. Then you’ll need to have an idea about Purusha, or Spiritman in the heavens (compare f.i. Adam Kadmon and Cabala). You can use the Veda-link on the right for further study.  Fire is his head, Sun and Moon are his eyes, his ears are the four directions in cosmic space.

Lastly you must know some background information about the Caste System. There are

• Arya;s, the Nobles, permitted to read the Weda’s
• Ksjatria’s, the wariors, princes, knights
• Sjoedra’s, the servants
• Brahmans, the teachers, the priests, the highest caste of them all
• Paria’s, lesser folk, slaves and outcasts
• Waishya’s, the merchants and landowners and farmers

Now in this framework you can study the Oupanishads and slowly expand your knowledge.