The eightfold path of Yoga (Astangha Yoga)

The founder of yoga is the sage Patanjali. He has written the Yoga philosophy in the Yoga Sutras (196 lines in 4 chapters) The second line of the first chapter reads:

“Yogah chitta vrtti nirodhah”

This can be translated as Yoga is the cessation (nirodhah) of the fluctuations (vrtti) of the mind (chitta).

The eightfold path of yoga is described in the Yoga Sutras. These are various stages, you will go through if you choose yoga as a way of life. It is not a strict hierarchy, but the phases are often simultaneous and certainly in changing order.

1 Yama
universal moral commandments, self-control with regard to the outside world (5); ahimsa – non-violence, satya – truth, asteya – do not steal, brahmacarya – chastity and aparigrahah – do not possess.
2 Niyama
purification of the self through discipline, self-control with regard to the own person (5); sauca – cleanliness, santosa – contentment, tapah – a burning desire, zeal, svadhyaya-study of the self and isvara pranidhanani-focus on Highest.
3 Asana
posture
4 Pranayama
rhythmic breath control
5 Pratyahara
freeing the spirit of the control of the senses and of the focus on outward objects
6 Dharana
concentration
7 Dhyana
meditation
8 Samadhi
a State of supra-or superconscious which is reached through deep meditation; in this condition the individual pupil, the one whom strives for the goal (sadhaka), becomes one with the object of his meditation-Paramatma or universal spirit, fully aware and vigilant.

With Yama and Niyama the yogi masteres his urges and emotions. Asanas keep the body healthy. The first three stages form the outward-facing search.
The next two stages, Pranayama and Pratyahara, teach the pupil to master his mind, the inward search.
The last three stages, Dharana, Dhyana and Samadhi, take the yogi to the inner, most hidden recesses of his soul.