Literal Meaning: Ashta (Eight), Anga: Limb. Ashtanga refers to the eight limbs (branches) of Yoga. Patanjali outlined the following eight aspects of spiritual yogic practice in his Patanjali Yoga Sutra.

1. Yama: Universal morality
2. Niyama: Personal observances
3. Asana: Body postures
4. Pranayama: Breath control
5. Pratyahara: Control of senses
6. Dharana: Concentration and cultivating inner perceptual awareness
7. Dhyana: Meditation
8. Samadhi: Union with the Divine

Brief on the Eight limbs of Yoga:

The first two limbs deal with the ethical principles and give suggestions on how to deal with ourselves and people around us. They generally discuss how we use our energy in relationship to others and ourselves.

Also, refer to the below link for more details :

http://www.swamij.com/yoga-sutras-22629.htm

1.Yama

This is the first limb of Ashtanga Yoga. It is about external discipline, the restraints and control.

Yamas are further broken down into five characteristics which are listed below:

1. Ahmisa: – Non Violence:
2. Satya: – Commitment to Truthfulness
3. Asteya:- Non-stealing
4. Brahmacharya:- Continence
5. Aparigraha: – Non Covetousness, Neutralizing the desire to acquire and hoard wealth

2. Niyama

Niyama means rules or laws. The Niyama describes the rules for self. They are not any kind of exercise but are more personal.

Niyama is also further divided into five observances:

1. Saucha: – Purity, Cleanliness
2. Santosha – Contentment
3. Tapas – Austerity
4. Swadhyaya – Self-study, study of scriptures
5. Ishwara Pranidhana – Surrender to God’s will

3.Asana

The literal meaning of Asana is to sit and refers to the practice of physical postures. The practice of Asana has multiple benefits the most underlying are improved strength, health and flexibility. On digging further, one will find deeper experience of calming one’s mind and exploring the mental attitude and strengthening the will power.

4.Pranayama (Breath Control)

Prana means (life,energy) and yama means to control. Pranayama is not just the breathing exercise but a means to direct or control the life energy.

Bringing awareness to breath helps in the manifestation or experiencing the consciousness. Pranayama is very important part of yoga and practiced while doing asana also.

5.Pratyahara (Control of the Senses)

Pratyahara means drawing awareness within, away from the senses and distractions.

The word ahara means “nourishment”,”food”; pratyahara translates as “to withdraw oneself from that which nourishes the senses.”

6.Dharana: (Concentration and cultivating inner perceptual awareness)

Dharana is concentration, keeping your attention riveted on one thing. Here mind is supposed to focus its attention in one direction instead of going out in many different directions

The objective in dharana is to steady the mind by focusing its attention upon some stable entity.

7.Dhyana: Meditation

Dhyana, or meditation, is an unbroken awareness or experience of the object of meditation.

8.Samadhi (Union with the Divine)

The final step in the eight-fold path of Yoga is the attainment of Samadhi. Samadhi means “to bring together, to merge.” In the state of samadhi the body and senses are at rest, as if asleep, yet the faculty of mind and reason are alert, as if awake; one goes beyond consciousness.

You can also refer the same here :

http://www.yogaoutlet.com/guides/the-eight-limbs-of-yoga

You can also, check more on Yoga from

Origination of Yoga

Or see why I have once again started Yoga:

Why I again want to start Yoga?