The Upanishad says that the self has four aspects. One is the waker, one is dreaming and another is deep sleep. Here we are studying Vedanta: Where are we? Waker and waking world. All of these are actually manifestations or appearances of this one consciousness - which is I.
Swami Sarvapriyananda teaches one of the shortest and most profound upanishads accompanied by Gaudapada's Karika. This lecture covers Mantra 5-6.