Brahmananda Valli
The statement "Brahmavida Apnoti Param" which means "The one who knows Brahman attains supreme state" is the formula (Sutra-Vaakya) to get the high level gist of this Valli. First Anuvak starts with Shanti Mantra "OM sham no mitra" and "Sahana vavatu" pleasing gods and removing obstacles for study of Upanishad being the objective of these Mantras. Second Anuvak starts with formula sentence "Brahmavida Apnoti Param" as stated above and also tries to define Brahman succinctly as "Truth, Omniscient, and Infinite" (Satyam Jnyanam Anantam Brahma).
Anuvaks Second to Fifth describe that Five sheaths subtle bodies or (Five Atmans) reside in one another in human body. Starting with grosser, tangible human body called "Annamaya" or "Formed out of Food" to "Pranamaya" or "formed out of Vital life force" to "Manomaya" or "Formed out of Mind" to "Vijnyanamaya" or "One who is of Knowledge" to Final and subtle most being "Anandamaya" or one who is full of Joy.
In Sixth and Seventh Anuvaks, some of the questions asked by a disciple are answered. such as
"Brahman being equal to both knower and ignorant, who gets the Brahman after death, knower or ignorant and why?"
Eighth Anuvak, compares happiness of various evolved beings starting from Man to that of next higher level till Happiness of Brahman itself.
Ninth Anuvak describes that knower of Brahman doesn't repent for not having done any good because for him/her, the terms good and bad loses their meaning and he/she has equalled them with Brahman since it is the only one which is really existing.
Read more about this topic: Taittiriya Upanishad