Compared to the Brihad-Aranyaka and Chandogya Upanishads, the Taittiriya Upanishad is a succinct little meditation on a few moral and metaphysical concepts. The first section primarily valorizes the relationship between a teacher and student, praising the wisdom that can be acquired in such a relationship. This conforms to a common interpretation of the word "upanishad," thought to mean to sit at the feet of, which also has led some to understand the upanishads as teaching an esoteric doctrine. Such an understanding is easy to accept today, when so much learning takes place through texts and other audio and video media; however, when the Taittiriy Upanishad was written, word of mouth teaching was the norm and did not necessarily imply an esoteric teaching.
At the same time, the teaching of the upanishads might very rightly be thought of as esoteric and necessarily requiring instruction from a "seer." The doctrines of the Upanishads themselves would suggest that not everyone is able to grasp their truth without the aid of a seer. Without initiation into the doctrines, most people would not question the reality of their perceptions. It is the rare person who will see beyond the empirical world and into the truth that lies behind it without the guidance of someone who has tread the path before.
The second section explains how knowledge of Brahman (or the divine reality) is bliss. Based first of all on a metaphysical idealism, the section asserts that the contents of the consciousness that constitutes reality is bliss. Here, one is reminded of Meister Eckhart's concept of god as love. Instead, reality is bliss.
The third section describes the Brahman as food. The overall impression is one of the ecological interrelated of nature and ultimately all of being.