In the West, yoga means standing on your head. In Hinduism, it means meditation. Yoga literally means meditation. " union".It's about uniting your attention with its source, your everyday awareness with the fountain of consciousness from which it springs.
Hindus thinkers were not into philosophy just to show off how smart they were. Even the driest Hindu thinkers of them all, the Nyaya logicians, had a sacred purpose in mind. That was to use their knowledge as a means to moksha, spiritual liberation. To Hindus, philosophy is never just an intellectual exercise as it so often is in the West. It's a door to the living experience of divine reality.
Yoga is practical branch of Sankhya, the spiritual techniques used to move from talking about higher levels of reality to actually experiencing them.
Sankhya says that everything in the ever-changing universe, including the energy out of which our minds are made, comes from prakriti, energy. Prakriti is the ocean of energy that exist forever in all dimensions of eternity. Its grossest manifestation is the physical matter we see' and touch.
> Rajas : Motion. Active, energetic, hot. Kinetic energy.
> Tanas : Inertia. Heaviness, dullness. Potential energy.
> Sattva : Harmony. Lightness, clarity. Balance energy.
When all three gunas balance each other, the universe melts away. It's like the mathematical equation {-1} +0+1=0 . But when the gunas fall out of equilibrium, a motion rolls through the cosmic ocean of primeval energy , and a new universe begins to form.
Yogis actively way to balance the gunas in their personalities so that they can disengage from matter completely and shift their awareness back fully into pure consciousness itself. When that happens , the karmashya, the baggage of karma the causal body carries around when it, falls away along with the causal body itself. The yogi is now liberated- free from karma and the cycles of rebirth. She has shifted her awareness totally into the twenty-fifth category of reality, purusha, the Inner Self.
The Sankhya masters stay there are an infinite number of purushas floating around the universe, trillions upon trillions of souls. The yoga system adds one more special purusha: God. According to yoga, God is divine consciousness that never fell into matter when the universe first formed. God has always existed outside time and space , but is so gracious he occasionally lends us a hand in our efforts to escape the eternal treadmill.
Purusha and prakriti, spirit and matter, never come into contact with each other in this system. Purusha doesn't " act" in matter. It can't because the power to act, our organs of action, belong to the sphere of prakriti. The Purusha is a ball of consciousness that merely observes. Have you been in an accident where your car was spinning out of control ? During emergencies, many people report they were thrust into a state of calm clarity they weren't afraid at all, but were simply observing what was happening. That tranguil inner observer is the purusha.