In Sanskrit "Ashta + anga" is ashtanga. "Ashta" means Eight and "Anga" is limbs so it means Eight Limb path, Ashtanga yoga is based on Yoga Philosophy of Patanjali.
Yoga has its roots about 5000 years BC as described in Vedic Philosophy and Tantras. The great sage Patanjali, composed this path into a Darshan (Philosophy) in his Book Patanjal Yoga Sutra. In which he has formulated Yoga as a Eight Limbs or Eight Fold path.
Ashtanga Yoga of Maharshi Patanjali provides the comprehensive understanding on the principles and practices of the subject with its scientific background. Commonly known as the 8 limbs of yoga, basically act as guidelines on how to live a meaningful and purposeful life. They serve as a prescription for moral and ethical conduct and self-discipline; they direct attention toward one’s health; they help us to acknowledge the spiritual aspects of our nature and achieve the highest state of Yoga, also known as Samadhi.
Maharshi Patanjali's eight limbs of yoga is as follows:
Yamas are ethical rules and can be thought of as moral imperatives (the"don'ts"). The five Yamas listed by Patanjali in Yoga Sutra are.
Patanjali also states how and why each of the above self-restraints helps in an individual's personal growth. For example, in verse II.35, Patanjali states that the virtue of nonviolence and non-injury to others (Ahimsa) leads to the abandonment of enmity, a state that leads the yogi to the perfection of inner and outer amity with everyone, everything.
The second limb of Patanjali's Ashtanga Yoga is niyama, which includes virtuous habits and observances (the "dos"). The Niyamas are as below:
As with the Yamas, Patanjali explains how and why each of the Niyamas helps in personal growth. For example, in verse II.42, Patanjali states that the virtue of contentment and acceptance of others as they are (Santosha) leads to the state where inner sources of joy matter most, and the craving for external sources of pleasure ceases.
Patanjali defines Asana (posture) in Yoga Sutra as follows,
Sthirashukhamasanam ॥
The meditation posture should be steady and comfortable.
Asana is a posture that one can hold for a period of time, staying relaxed, steady, comfortable and motionless. The Yoga Sutra does not list any specific asana. "Asanas are perfected over time by relaxation of effort with meditation on the infinite"; this combination and practice stops the body from shaking. Any posture that causes pain or restlessness is not a yogic posture. Secondary texts that discuss Patanjali's sutra state that one requirement of correct posture for sitting meditation is to keep chest, neck and head erect (Proper spinal posture).
Over a thousand years later, the Hatha Yoga Pradipika, mentions 84 asanas taught by Lord Shiva, stating four of these as most important: Siddhasana (accomplished), Padmasana (lotus), Simhasana (lion), and Bhadrasana (glorious), and describes the technique of these four and eleven other asanas. In the Modern Yoga asanas are prominent and numerous, unlike in any earlier form of yoga.
Pranayama is the control of the breath, from the Sanskrit Prana means Vital energy and Ayama means restraint or Expansion .
After a desired posture has been achieved, Patanjali recommends Pranayama, the practice of consciously regulating the breath (inhalation, the internal pause, exhalation, and the external pause). This is done in several ways, such as by inhaling and then suspending exhalation for a period, exhaling and then suspending inhalation for a period, by slowing the inhalation and exhalation, or by consciously changing the timing and length of the breath (deep, short breathing).
Pratyahara is a combination of two Sanskrit words Prati means "against" or "contra" and Ahara means "bring near, fetch".
Pratyahara is drawing within one's awareness. It is a process of retracting the sensory experience from external objects. It is a step of self- extraction and abstraction. Pratyahara is not consciously closing one's eyes to the sensory world; it is consciously closing one's mind processes to the sensory world. Pratyahara empowers one to stop being controlled by the external world, fetch one's attention to seek self-knowledge and experience the freedom innate in one's inner world.
Pratyahara marks the transition of yoga experience from the first four limbs of Patanjali's Ashtanga Yoga that perfect external forms, to the last three limbs that perfect the yogin's inner state: moving from outside to inside, from the outer sphere of the body to the inner sphere of the spirit.
Dharana means concentration or one-pointedness of mind. The root of the word is Dhar meaning "to hold, maintain, keep".
Dharana, as the sixth limb of yoga, is holding one's mind onto a particular inner state, subject or topic of one's mind. The mind is fixed on a Mantra, or one's breath/navel/tip of tongue/any place, or an object one wants to observe, or a concept/idea in one's mind. Fixing the mind means one-pointed focus, without drifting of mind, and without jumping from one topic to another.
Dhyana literally means "profound, abstract meditation".
Dhyana is contemplating, reflecting on whatever Dharana has focused on. If in the sixth limb of yoga one focused on a personal deity, Dhyana is it’s contemplation. If the concentration was on one object, Dhyana is non-judgmental, non-presumptuous observation of that object. If the focus was on a concept/idea, Dhyana is contemplating that concept/idea in all its aspects, forms and consequences. Dhyana is uninterrupted train of thought, current of cognition, flow of awareness.
Dhyana is integrally related to Dharana, one leads to other. Dharana is a state of mind, Dhyana the process of mind. Dhyana is distinct from Dharana in that the meditator becomes actively engaged with its focus. Patanjali defines contemplation (Dhyana) as the mind process, where the mind is fixed on something, and then there is "a course of uniform modification of knowledge".
Adi Shankara, (a most know Vedic scholar) in his commentary on Yoga Sutras, distinguishes Dhyana from Dharana, by explaining Dhyana as the yoga state when there is only the "stream of continuous thought about the object, uninterrupted by other thoughts of different kind for the same object"; Dharana, states Shankara, is focused on one object, but aware of its many aspects and ideas about the same object. Shankara gives the example of a yogin in a state of dharana on morning sun may be aware of its brilliance, color and orbit; the yogin in dhyana state contemplates on sun's orbit alone for example, without being interrupted by its color, brilliance or other related ideas.
Samadhi literally means joining, combining with, union, harmonious whole, trance". In samadhi, when meditating on an object, only the object of awareness is present, and the awareness that one is meditating disappears. Samadhi is of two kinds, Samprajnata Samadhi, with support of an object of meditation, and Asamprajnata Samadhi, without support of an object of meditation.
Samprajnata Samadhi, also called Savikalpa Samadhi and Sabija Samadhi, meditation with support of an object, is associated with deliberation, reflection, bliss, and I-am-ness.
Patanjali describes this eighth and final stage of ashtanga, samadhi, as a state of ecstasy. At this stage, the meditator merges with his or her point of focus and transcends the Self altogether. The meditator comes to realize a profound connection to the Divine, an interconnectedness with all living things.