"Yoga" signifies many things: Higher states of consciousness that differ from our everyday waking life; a higher state of being; knowing ourselves in a more pure form; the actual "practice of yoga" which helps us reach these higher states of consciousness.
Yoga is a path to experiencing and realizing our True Nature. This is the path of Self-realization. It sounds all grand and lofty and we often say to ourselves: "Yah... right. Not today. I just want to be more active, lose a few pounds and get rid of my low back pain."
I understand that. I began the practice for the physical aspect in 1997 first for those very reasons, and found, pretty quickly, that my mind, the mental aspect, was also impacted positively. I felt a stronger sense of clarity and concentration as a result of the physical practice. I didn't let myself go past the physical and surface mental levels until my 9-day-old son passed away and I needed answers.
So, I want to let you know, I'm with you if you're skeptical and just want to feel better physically and experience less stress. I will add that devoting yourself to the physical practice itself will deepen your overall practice over time.
Yoga practice helps us answer the big questions. What I really want to say to you is that the questions we ask ourselves, the deeper questions, are no different from what Yoga helps us realize.