The Sanskrit word yoga has many meanings, and is derived from the Sanskrit root "yuj", meaning "to control", "to yoke" or "to unite". Translations include "joining", "uniting", "union", "conjunction", and "means". It is also possible that the word yoga derives from "yujir samadhau," which means "contemplation" or "absorption." This translation fits better with the dualist Raja Yoga because it is through contemplation that discrimination between prakrti (nature) and purusha (pure consciousness) occurs. (Wikipedia)
Many people have a limited understanding of yoga, thinking that it is restricted to the asana practice of increasing flexibility, toning up muscles, relaxing the body, increasing strength, improving balance and finding stress relief. While yoga does all of the above that is a limited view of what yoga really has to offer us. The true purpose of yoga is to develop a relationship with the self that exists deep within our core, which is called Jivatman (individual soul). Jivatman is a unity of Atman, the supreme soul, or Brahman, that is always there, unchanging and endlessly radiating the energy of peace, love and compassion.
According to the Upanishads, our human nature, or prakriti, is comprised of five different dimensions. Our mortal body, (the temple of our individualized atman) expands into more subtle layers of energy around our spiritual center. Human beings consist of five distinct energy sheaths called “koshas” that surround our jivatman. Each kosha vibrates at different speeds, and they interact and overlap with each other, ranging from gross to transcendental dimensions.
The pancha koshas (five sheaths) provide us with a road map for better understanding of our psychological and spiritual development. There are namely:
Physical – Annamaya kosha
Energy – Pranamaya kosha
Mental – Manamaya kosha
Wisdom – Vijnanamaya kosha
Bliss – Anandamaya kosha
Self – Atman
Figure 1.6 - From One Mind comes all. All goes back to One Mind
2.24 - The Duality of One