Yoga in the world today is often described as 'the yoga tree'. At the centre is the trunk, the solid core and tradition of yoga. It's roots stem deep into the ancient earth with its ancient philosophy and wisdom. Thick branches stem from the trunk, leading to thinner branches, twigs and leaves. Some of them intertwine and grow together. Others grow in completely different directions. That is why we have everything from devout practitioners retreating to meditate for months in remote caves to flashy, trendy yoga practiced to a background of hip hop and pop music.
Yoga Lineage flow chart Here is a great visual description of yoga lineages. It helps to have a picture of where your yoga is coming from, and which branch of the yoga tree you're sitting on.
Here is another great link. Krishnamacharya's Legacy is a fantastic article by Fernando Pages Ruiz, published in yoga journal. In fact, www.yogajournal.com is an amazing yoga resource and has hundreds of good quality articles to help deepen your understanding of yoga practice and philosophy. It is one of my favourite resources.