What is Yoga?
The Sanskrit word "Yoga" means "Union". Union with what you may ask? I would suggest as a starting point, union with your self. Yoga can be seen as a complete science of life in that it incorporates so many depths and facets a lot which you do not seek but just stumble upon as you practice. As your body opens up, many of the blockages and old habits you develop from birth start to shift and change till your subconscious and consciousness begin to merge.
In practical terms yoga is a system of postures aimed to stimulate the glandular, lymphatic, nervous, muscular and skeletal systems to cleanse, massage and elongate the body, eliminate toxins and to operate with increased vigour and vitality. In this respect yoga can be used to address a whole host of health issues.
Enjoyment is the key! If wrapping your legs behind your head is your goal then go for it, if you merely want more slender thighs then regular practice can lead you to leaner legs. If you want to de stress yoga can help with this.
In summation, whatever your motivation with an open mind, yoga will help you lead a better lifestyle and that is as good a reason as any for going to your first yoga class.