Ashtanga means Eight Limbs. To be practicing Ashtanga Yoga you must practice all 8 limbs. We must always remember that Asanas (postures) are only one aspect of this practice, and we need to look into how to include all limbs to become Ashtanga practitioners. The Ashtanga yoga practice which was systemised by Sri K Pattabhi Jois
Ashtanga means Eight Limbs where ashta = eight and anga = limbs. Ashtanga is the Eight Limbed path of yoga.
The eight limbs of yoga are prescribed to us by Patañjali in the ancient Yoga Sutras.
The eight limbs which if perfectly followed consistently and for a long period of time (most likely lifetimes) will lead us to Samadhi and or Moksha (liberation). It is considered a science to liberation or what in the west we call enlightenment. The Limbs are as follows;
YAMAS These are five observances and behaviours which regulate how we behave to others
NIYAMAS These are the five commitments to ourselves and principles that we should follow.
ASANA Asana means comfortable seat. The postures made in practice are called asanas
PRĀNĀYĀMA Control of pranayama through breathing techniques
PRATYĀHĀRA Withdrawal of senses from objects
DHĀRAN Intense concentration
DHYĀNA Closest translation is meditation
SAMĀDHI A difficult word to translate as few have experienced it. Can be described as highest state of conciseness, liberation from samsara or karma.
The first four limbs are something that we can practice actively, i.e. they take place on an external level. When the first four limbs are strong within the Sādhaka (spiritual seeker), eventually the other four gradually take place internally within him or herself.
following this system is meant to be a way to samadhi or moksha liberation
If one is not following the eight limbs they are not practicing ashtanga yoga. Asana alone, without consciousness and breath control is not yoga, it is no more than gymnastics.