What is yoga?
In the West, yoga is typically associated with hatha yoga which is practiced in studios and gyms around the world using a technique that includes breath control and various stretching poses to develop a sense of calm and physical well-being. The word yoga has several meanings. One definition is “a means to unite, join or connect with the destination.” Yoga can also be described as "control or mastery of something.” A third meaning is “topic” or subject matter. Each of the chapters of the Bhagavad Gita is traditionally titled in Sanskrit using a compound word that includes yoga, so that, for example, the fifth chapter is called Sannyasa-yoga or “The chapter on the topic of renunciation.”
Vedanta defines spiritual life as two stages: there’s a stage of action (yoga) for doers, and a stage of knowledge(jñana) for inquirers. The former is a preparation for the latter. Thus, all seekers begin looking for freedom as doers. The first stage helps to purify the mind and make it introverted. Each yoga or discipline mentioned in the Gita has its particular purifying function. For example, karma yoga helps manage the ego, dhyana yoga helps cultivate focus, and bhakti yoga helps center emotion.
Yoga, as various spiritual practices, is said to eventually lead the individual to experience oneness with the Self. Shankaracharya, an early proponent of Advaita Vedanta, redefined it as complete absorption in the thought, "I am awareness and not the body-mind" (see Aparokshanubhuti by Shankaracharya).