The word Yoga belongs to Sanskrit language. It is derived from the root word, 'Yuj' which means "to join". Probably this is what the Yoga Practices in the present century suggests to. That is to join the individual with the divine!
Yoga has several definitions. Its functions and character can be defined in hundreds of ways. One of the short and meaningful definitions of yoga is "Efficiency in work is yoga."
As for the action-oriented explanation of yoga, any action that you do with the motivated desire is not yoga because its results are impermanent! Action done with a pure mind, with total surrender, without worrying over the fruits of actions is yoga.
Every action has a reaction. And the intensity of the reaction is in proportion to the intensity of the action! Even the scientists agree on this principle. One of the rare agreements between the scientists and the spiritualists! Normally, the two opposing forces- the two contending forces!
When you understand this fundamental principle, why worry over the results of your actions? Why worry over the matter, over which you should not worry at all!
Patanjali, one of the most revered Sages of India, is the father of Yoga. He wrote the immortal book, based on his practical experiences and the divine vision! His writings and practice have found worldwide acceptance now! He wrote the book about 2500 years ago!
Yoga has the body aspect, the mind aspect and the beyond the mind aspect, which is also known as the transcendental level! This level could only be experienced by an individual. It can't be explained by words!
Sage Patanjali has mentioned eight sutras: They are: Yama, Niyama, Asana, Pranayama, Pratyahara, Dharana, Dhyana and Samadhui.
The asanas refer to various physical postures. This aspect of Patanjali's yoga has become very popular in India as well as abroad! According to the claims, there is no disease that can not be cured by practicing these asanas. If you practice some specific asanas, no disease will ever come near to you.
The last sutra, Samadhi is the supreme goal of the individual. There is nothing beyond to achieve for a human being. It is "be all and end all."
You need to learn these asanas from a qualified teacher. Some of the asanas are difficult physical postures, and if done without proper knowledge about their intricacies may cause more damage. Start slowly, and do the asanas in accordance with your physical capacity!
All your problems of the modern industrialized civilization such as stress, tension, confusion, blood pressure and all negative tendencies will leave from the back door, once you come into the thick of yoga! They will never return, they will go for ever!
"Yoga is what yoga does!"