Asana is a Sanskrit word meaning, "seat"... and also the third limb of yoga as per Patanjali's Yoga Sutras.
In shaping our bodies into these postures, they become a tool to unite breath, body, and mind; merging our sacred humanity with our innate Divinity and returning us to a state of Conscious or Loving Awareness.
We use the physical practice of Yogasana to prepare ourselves for the deeper practices of Yoga, such as pranayama (breathing) and meditation.
Patanjali describes the Eight Limbs of Yoga as:
The Yamas are rules of moral code and include ahimsa (non-harming), satya (truthfulness), asteya (non-stealing), bramacharya (sexual restraint/self moderation), and aparigraha (non-possessiveness).
The Niyamas are rules of personal behavior including saucha (purity), santosha (contentment), tapas (discipline or austerity), svadhyaya (spiritual studies), and Ishvara Pranidhana (constant devotion to God).
Asana refers to yoga postures but in Patanjali’s initial practice, it referred to mastering the body to sit still for meditation. The practice of yoga asanas came about eight centuries later, which helped disciples ready their bodies for meditation.
Pranayama are yoga breathing techniques designed to control prana or vital life force.
Pratyahara means withdrawal of the senses.
Dharana refers to concentration.
Dhyana is the practice of meditation.
Samadhi is merging with the divine.