Can you explain the concepts of Maya, Purusha, and Brahman as they are detailed in Chapter 19?

Chapter 19 provides a hierarchical description of reality. It explains that the Soul is a Great Power, but subtler than the Soul is the Unmanifest (Avyakta), which is also called Maya or Unmanifest Nature. The text states that even subtler than all these is the Purusha, the Supreme Being. This Purusha is described as the ultimate goal where the senses and mind find rest, and it is identified as the Pure Brahman. The Soul, though itself changeless, appears in this world according to the actions of Maya, much like a pure crystal seems to take on the color of things near it.