As per Taittiriya Upanishads body is composed of 5 layers. They are Physical, Energy, mind, intellect and bliss levels. There are yogic practices which were useful to protect from climatic changes. Hence the person lives in tune with the climate and was aware of the God (creation) all the time. This was the lifestyle than the special session of the day. As per the mind and its fluctuations (emotional attachment) person changed the way he lives and changed the practice and became dependent on assistive devices. Hence the styles of Yoga has come into the world. There are so many styles having basic principle behind. But as mentioned earlier, the names and practices are changed to attract the world. Let us discuss few styles here.
1. Hatha Yoga: Very old and traditional method. It has all practices related to all 5 levels of existence. It suits everyone at any age. It has the sequence to raise and balance the metabolism.
2. Ashtanga Vinyasa Yoga: This is recent than Hatha Yoga. It is intense and keeps the high metabolism. This is built by Sri. K. Pattabhi Jois for natural purification of Mind and Body. Natural purification is good, but what happens if it is every month of the year? Physical and breath level are very much used. But it does not have the emphasis on meditation techniques to relax the mind.
3. Vinyasa Yoga: Movement synchronize with the breath is a good concept. But this is also continuous flow. More emphasize on Physical practices and the rest are from Hatha Yoga tradition.
4. Iyengar Yoga: Initial steps are the base for future. This concept makes the spiritual journey. So BKS. Iyengar brought the concept of alignment and assisting techniques, so the benefit will be fulfilled from asana. Hence there are no emphasis on pranayama, meditation and kriya techniques. Those should be followed from Hatha Yoga tradition.
5. Vini yoga: This developed by TKV. Desikachar. This is truly individualized practice. This is a style of Hatha Yoga with the concept of body, breath, mind and its meaning during practice. Much emphasize on stretching exercises. The rest techniques are as Hatha yoga.
6. Shivananda Yoga: This is the form of Hatha Yoga. They techniques flow is different from traditional Hatha Yoga. Hence this has the balancing metabolism according to the climate.
7. Power Yoga: It imitates Ashtanga Yoga but the sequence is not prepared like Sri. K. Pattabhi Jois. This is just to grab the attraction of westerns. So, it Is Physical.
8. Bikram Yoga: Since the temperature is artificially provided for the body throughout the practice time, the metabolism has to come to resting metabolism at the natural climatic conditions. Hence there will be very good stretching of the muscles, but more length than required. It leads to deformities because of overlengthening of muscles.
9. Yin Yoga: since the metabolism again is the concept, the muscles as stretched for long times and get the poor posture as in Bikram Yoga. This is also good for the initial stage of practice to get required flexibility, but later it worsens the body movements.
10. Tantra Yoga: This is mental practice. This is the best practice for couples means, specific to some group. Hence can not be for all. This is the practice of Brahmacharya with all stimulants around. Brahmacharya against stimulus is good, but it is separate from rest of the day. This can not be a lifestyle.
11. Integrative yoga Therapy: This is made as a treatment for diseases. But once the disease has reduced, techniques should be changed. That would, of course, be Hatha Yoga.
There are some more names and techniques. When there is an old technique by name Hatha Yoga given by ancient sages, why so many names do has come into this world. This is the attachment for name, fame, and money. Yoga became special practice than Lifestyle. It has become a business with different names. An ordinary person should know about this. Youngsters who are entering this field should be guided about this. A recent research says different styles do not differ in their odds of reaching positive conclusions (https://www.ncbi.nlm.nih.gov/pubmed/27062966). Choices made available while introducing ancient wisdom. Hence the person does not have information about the core essence of Yoga as a lifestyle, or if the person does not know the path of spirituality is yoga, then it is misleading. Educating people is mandatory especially, youngsters.
Yoga is a lifestyle but not the practice.