Elements of Yoga : Yoga is not a mechanical process but a thoughtful process. The main purpose of yoga is to provide a sound body with tension free and sound mind. The ultimate aim of yoga is self-identification and self perfection which comes through self realization and self purification. According to Patanjali, Yoga consists of 8 (eight) stages to achieve the union of Atma with Parmatma. Patanjali outlines a complete eight fold path that deals with all elements of Yoga in our life inwardly and outwardly.
The elements of Yoga are :
(i) Yama : These are the basic principles, codes of ethics or restraints such as honesty, non-violence, non-stealing and non-possessiveness. These are universal commandments. These restraints are meant to prevent a person from indulging in undesirable worldly activities. 
(ii) Niyam : These are basic principles for self, like a healthy body, hygienic habits, proper diet, sleep, rest, work routine, etc. This is a self moral code of discipline. We call it lifestyle development.
(iii) Asana : These are slow stretching activities performed to improve the whole body fitness. Asanas are the postures which keep the body healthy, balanced and helps it in maintaining harmony with nature.
(iv) Pranayama : This is a systematic and rythmic control of breathing, performed to improve the functioning of the body. It is a breathing exercise which includes breath in, retention and breath out and then relax.