Fourteen Lokas as Viewing Galaries

Puranas describe fourteen worlds or Lokas which includes the Earth plane. Seven of the fourteen are below earth plane and six are above it. Earth plane is the boundary marker between upper and the lower planes of existence. Planes of existence are parallel realities which are embedded in this very cosmos. Some experts asign lower life forms to lower planes of existence. There is, for example, a world within our body. Every cell in our body is intelligent with a constrained zone of movement. The lowly earthworm, n the other hand, has an independent existence. Its life span is limited and it experiences tiny space in the ground. Human beings exhibit several orders higher intelligence. Vedic texts count 84,000 species and assign them to one of the fourteen Lokas. Pure energy beings exist in higher six planes per Vedic view as abstractions. The highest plane of existence is Satya Loka or the plane of Brahma. Highly evolved beings exist there.

A soul gains a body based on its past Karma. Kathopanishad refers to three higher planes of exisence in one of its verses. This verse provides us an opportunity to understand the basis for fourteen planes of existence in terms of levels of consciousness. It discusses types of birth which are conducive to gaining liberation. Nirvana refers to knowledge of one's higher self, the knowledge of Brahman, A being reaches Pitru Loka or Gandharva Loka after missing the Nirvana opportunity in its human birth. A being who has not satisfied its craving for material comforts moves to the Pitru plane of existence. It hangs out there until its next human birth. Similarly, a being with unsatiated craving to enthrall others reaches the Gandharva plane of existence. 
Kathopanishad 6th Valli

Kathopanishad explains why it is impossible for a being to attain Nirvana in its Gandharva and Pitru births. It considers planes of existence as vantage points which provide different views of Brahman. One can compare the vision of Brahman in Pitru plane to a dream vision if one compares the vision of Brahman in human plane to a reflection in a mirror. The clarity of a reflection is limited by the quality the mirror. A dusty mirror provides a hazy view while a polished mirror provides a clear view. Human mind which has been cleared of cravings and aversions acts like a polished mirror. However, a dream vision is always vague. Knowledge of Brahman is elusive in Pitru Loka because the memory of a dream is even more vague. The vision of Brahman in Gandharva loka is like a reflection on the surface of  agitated waters. Bright lights dance on water surface and distract a viewer's mind away from any reflections on the surface of water. A clear vision of Brahman is possible only in Brahma Loka.

Brahman appears as Light and Shadow in the highest plane of existence. The nature of Brahman is light and shadow. Shadow vanishes when light vanishes. The dynamic portion of existence is unreal per Upanishads. It is like a shadow. The static aspect of existence is consciousness. Light and darkness exist togather in Brahman. Material creation and consciousness coxist withn creation. The former however cannot exist independently. Human plane of existence provides direct glimpses into this truth. Yogis strive for repeated experience of this truth. They culture their nervous system with such experiences and transition to Brahma Loka.