What is Ashtanga Yoga?
What is Ashtanga Vinyasa Yoga?

Ashtanga is the combination of two Sanskrit words: Ashtau means eight and anga means limbs. Ashtanga Yoga is the systematic way in which yoga occurs as described by the sage Patanjali in the Yoga Sutras.The eight limbs are seen as a progressional development of the self that ultimately lead to Yoga (union).

The eight limbs are:

Yama - interpersonal actions
Ahimsa - non-violence
Satya - truthfulness
Asteya - non-stealing
Bramacharya - balance of actions (abstinence)
Aparigraha - non-covetousness

Niyama - Personal actions
Saucha - Purity/cleanliness
Santosa - contentment
Tapas - spiritual austerities
Svadhaya - study of self
Ishvara Pranidhana - surrender or devotion to god

Asana - physical poses

Pranayama - breathing techniques

Pratyahara - sense withdrawal

Dharana - intense concentration

Dhyana - meditation

Samadhi - bliss or state of yoga(union)

Ashtanga Vinyasa Yoga primarily focuses on the physical postures but also realizes that practice of the physical in a certain way also develops and prepares one for understanding and practicing the rest of the eight limbs. It should also be understood that Sri K. Pattabhi Jois (my interpretation) makes absolutely no differentiation between asana and the eight limbs of Patanjali. In other words you cannot seperate it from the others. When he says Ashtanga, he is referring to Patanjali's Ashtanga.

It should also be noted that the first four limbs are mostly observed externally while the last four are primarily internal practices.

The most important aspect and one that differentiates this practice from other styles of yoga is "Vinyasa" which means breath movement coordination or breathing system. In Ashtanga Vinyasa yoga all the asanas along with the transitions into or out of them are associated with either an inhalation or exhalation. One should never hold the breath during the practice.