Yoga - it means "bridle" in Russian. First of all, yoga is aimed at ensuring that a person is able to "bridle" himself, i.e. control yourself. Yoga appeared before the advent of writing in India, so it is not possible to establish its age. But it is known that it already existed 5,000 years ago.
Apparently, when a very long time ago yoga was born as a set of exercises for brahmanas, who, due to the nature of their activity, had to sit for hours in one position during prayers, sing religious ginmas, etc. etc.
Over time, yoga ... well, not that it separated from brahmanism, but rather expanded greatly. So, for example, Indian Muslims began to practice yoga, which obviously has nothing to do with either Brahmanism or Hinduism. Since yoga as such did not have a pronounced religious component, it became available to the general population, regardless of their religion. Although, if desired, in yoga you can find many ts. "traces" of Hinduism.
Apparently, over time, yoga made a qualitative leap, going beyond the complex of physical exercises. Practicing yoga in itself heals not only the body, but also the mind. In particular, it relieves anxiety, stress, not too neglected neuroses, etc. Without any magic. Over time, the influence on consciousness became an end in itself for some followers, gradually overshadowing the initial goals of yoga.
Yogis are different. For example, the Hare Krishnas also consider themselves yogis (although for a layman it is generally not clear what is common between them and some followers of Ashtanga Yoga). In general, different types of yogas do not contradict each other, and in principle should be combined. a large number of different schools of yoga, and each school has its own proportions. Types of yoga, offhand:
Of course, for such a long time yoga could not help but acquire its own mythology. Well, when white-skinned barbarians began to spread information about it ... in general, not everything that is said about yoga is true. For example, "the unification of a separate human soul with the Soul of the Universe" from Olga's answer is a fresh myth that has nothing to do with yoga (in yoga there is no concept of "soul of the universe" at all, and there is also no concept of "soul", but there are as many as 3 concepts in which the Europeans are trying to discern the soul, they get confused, and then a fertile field for conjectures begins ). In principle, for a start it is enough to know that yoga is not related to magic, does not provide and cannot provide a place in paradise (or some analogue of paradise), and is ill-suited to solving everyday problems. Well that is of course, a calm, balanced and physically healthy person will probably cope better with some part of everyday problems, but yoga is not a universal solution for everything and all yoga is not.
Yoga is one of the ways of knowing yourself, the world and God. This path is certainly not one. The path of yoga, according to those who have passed it and are following it, is very difficult. There are two major stages in yoga: preparing the body and mind for yoga and yoga itself. The result of yoga practice is to see yourself and the world as a whole. An ordinary person has a narrowly focused consciousness. A person who has reached certain states is able to see the answer to any of his questions, simply by thinking about the question. The essence of yoga exercises is to learn to concentrate to such a state.
Literally the word "yoga" is translated as "unity". This refers to the unification of a separate human soul with the Soul of the Universe.
To achieve success in the path of yoga is possible only by immersing yourself in it, getting sick with it. Yoga requires a certain fanaticism. However, just by regularly performing asanas, you can achieve considerable results, for example, perfect health.
The famous "Soviet" yogi Slava Kurilov reached the highest states of yoga (enlightenment), doing it for about 10 years. For the first 5 years he performed only asanas, from 2 to 8 hours daily. Later he took up breathing and concentration, which led him to such states as levitation, enlightenment, flying in a dream, memories of past lives. You can read about his path in yoga in his own book (published diaries) "Alone in the Ocean".