My focus on teaching and learning yoga (even as a teacher) is on pranayama or the science and art of breathing. Having been a chronic asthmatic, I have personally experienced how yoga has allowed me to breathe full, free and easy. The impact this has on energy levels, stability of mind, lowering stress while improving physical health and fitness is simply incredible.
Yoga truly is a health modality that is holistic, integrating body, breath and mind. It holds many benefits in the areas of cardiovascular (heart), digestive (liver, kidney, intestines, etc.) and neurological (mind, read 'mental health' issues) and many other systems.
Let me also dispel some frequent misconceptions 'newbies' have about yoga:
1. That it involves incredibly difficult postures
2. Therefore, that it is mainly done by the young and flexible.
It is unfortunate that these are the pictures one often sees in the media. The reality is that you can start practicing yoga regardless of your age and even if (and I would say, especially if) you are unfit or unhealthy.
Know thyself is what Socrates said and applies just as equally to how you should approach your own yogic journey.