Patanjali, a great yogic sage, wrote “the Yoga Sutras” in essence a guide to our practice of yoga. Within the Sutras he described five afflictions or obstacles which are the main cause of our suffering and pain. The Kleshas are often depicted as a tree with Avidya (ignorance) as the trunk of the tree from which the branches or Asmita (Ego), Raga (attachement), Dvesha (aversion) and Abihinivesah (fear of death) sprout.  So far we have considered Avidya which translates as ignorance and Asmita, the ego.
Avidya, ignorance comes in the form of a mis-understanding of reality, an incorrect comprehension of a situation which causes us to act either consciously or unconsciously or perceive in a way that is mechanical, without conscious thought.  This mechanical way of being is born out of habits that have formed over years and it acts as a fog obscuring our sight like a steam mists up a mirror and makes us unable to see our reflection.

Avidya is not easy to recognise in our lives. We tend to notice it more from its absence than its presence. When we see something correctly we feel peace inside. No tension, no unrest, no agitation. The fog of avidya is lifted. This is what we are trying to achieve with yoga, to cease the endless turnings of the mind, to be at peace.

Patajali understood that it was difficult to identify with Avidya but that there were other troubles, obstacles that caused our ignorance that we could identify with more readily. Namely the ego (asmita), raga (attachment),  dvesha (aversion) and fear (morespecificatlly fear of death (abhinivesah).