Adi Shankaracharya had a strong faith in the philosophy of Advaita Vedanta. Advaita is a term which basically means identity of the self (which is more commonly referred to as 'Atman') and the Whole (Brahman). Adi Shankaracharya took the initiative of promoting the doctrine of Advaita Vedanta, which is based on the concept of non duality. The beliefs & philosophies of Adi Shankaracharya formed the base for the Smarta tradition or Smartism.
The Shankaracharya philosophy of Advaita Vedanta was originally called
the forest philosophy. It is due to the fact that, this philosophy was
so sacred that it wasn't really allowed to be preached to other people.
Infact, this philosophy was practiced only by the monks who lived in the
forests. These monks later on passed it to other ascetics.
Sankaracharya strongly believed in the importance of Vedas. He promoted
Hinduism and laid emphasis on the significance of Vedas. It happened at
a time when Buddhism and Jainism were increasingly gaining popularity.
Talking about the teachings of Sri Sankaracharya, he always said that,
spiritual ignorance is often caused when we tend to see the self and
that too at a moment, where self is not important or does not even
exist. He said that, it is of prime importance to draw a line and
distinguish between the right and wrong.