The word yoga is derived from the sanskrit word ‘Yuj’ ,meaning to unite, deeply indicating the union of jeevatma (soul) and Paramatma (universal soul). Yoga literally means union. It is a union of breath to the body,of the mind to the muscles and most importantly of the self to the divine. The practice of yoga leads to health in the body, peace in the mind, joy in the heart and liberation of the soul. It is the most secular and universal system for human salvation. It provides a complete system of self transformation and self realisation, which are the ultimate goals of human existence.

Patanjali (The compiler of the Yoga Sutras) defines yoga as a state in which there is complete elimination of thoughts (Chitta vritti Nirodha) and modification of the mind.

He introduces eight limbs of yoga (ashtanga)
Which are:
Yama & Niyama : Laws and principles which make you worthy for this society

Asana & Pranayama : Balance your body and mind,strengthen you physically and mentally, improve your immunity and melt unwanted fat

Pratyahara, Dharana, Dhyana and Samadhi : The step by step advanced spiritual practices. Leading to moksha and the bliss.