The Yoga Sutra, ascribed to Patanjali, is a concise summary of the Classical Yoga psychotechnology. We can call it psychology due to its deep delving into the shape and structure of mind, and the way we experience the world. We can call it technology because of the practical methods it offers to traverse the mind, and to make us ready for final liberation. In fact, the Yoga Sutra is so technical that it takes a lot of study to truly understand it. A guide is essential, for there are many important aspects of Classical Yoga technology that the Yoga Sutra merely hints at. It is a map that, at times, gives only general directions; at other times it provides crystal clear explanations.
The second line of the Yoga Sutra sums up the purpose of Classical Yoga. It tells us exactly what yoga is: yogas-citta-vritti-nirodaha. These four words – yoga citta vritti nirodah – cannot be easily and succinctly translated into English; in general, the sloka tell us that yoga is the cessation of the fluctuations of the mind. Yoga is a way to stop the mind’s movements but what is meant by mind and what is meant by fluctuation and just how do we stop them? These answers are provided.
The Yoga Sutra uses the term citta as the overarching term for what, in the West, we would simply call the mind. Iyengar  offers a detailed view of the various aspects of citta in his book Light on Life. Citta itself means consciousness, in its various manifestations. There are three major forms of citta. First, there is the lower mind’s consciousness, called “manas.” Manas is our perceptions, as we have seen in the Samkhya psychocosmology. Second, there is ahamkara. Ahamkara literally means “I-shaped,” according to Iyengar. It is ahamkara that gives rise to our ego and our mistaken view of self. And third, there is buddhi or intelligence, which is the first manifestation out of the cosmic consciousness called “mahat.” Manas and ahamkara are the outward-facing projections of consciousness. Buddhi turns us around and looks inward.
Vritti means whirlings, turnings, or fluctuations. Nirodah means restriction, death, or stillness. Although the Yoga Sutra provides a methodology for stilling the mind, before that is explored, an unspoken question is answered – “Why would we want to do this?” The answer is tadadrastruhsvarupevasthanum. When the mind is still, the seer can rest in her true nature. Now, before we learn how to still the mind and come to this rest, the Yoga Sutra provides a deeper view of the mind and the problems we face in trying to look behind it.