Sri Adi Shankaracharya is believed to be an incarnation of Lord Shiva. He is the world's greatest Guru (Jagathguru). He preached Vedic knowledge and awareness by teaching judgment, intellect and he instituted the worship of deities as worshipping different forms of the one God.
Legnd behind Shankracharya Jayanti :
About 2500 years ago, when the mankind was not living in harmony with their intrinsic spirituality and holiness, all the deities and rishis went to Mount Kailash and requested Lord Shiva to revive the world. Lord Shiva approved to their request and informed them that he would be born into the world.
In a little village, Kaladi, Kerela, Adi Shankaracharya was born to the Nambudri Brahmin couple, Shivaguru and Aryamba. The couple was remained without a child for a long period of time and prayed for a child or children. Shiva, then appeared to the couple in a dream and assured them a option of a son who would be having a short life, but the most brilliant philosopher of his day, or many sons who would be average at finest. The couple opted for a brilliant, but short-lived son, and thereby Shankara was born.
Shankarachrya travelled and explored for a virtuous Guru who would commence him and acquire his determination of sanyasam (monk). He found the Ashram of Govinda Bhagavathpada who was recalled as Patanjali in a preceding birth. Govinda Bhagavathpada was also the follower of Goudapada, early and most reputed philosopher of the Vedanta school of thought.
Govinda accepted Shankara as his disciple. He commenced him into the uppermost kind of renunciation. Shankara was taught various Vedas as well as advaita. Advaita is the principle that each and every creator on this earth is the demonstration of God and that God and soul are one and the same. He guided Sri Shankara to go out into the world and make everyone aware of this truth throughout the country, which he did.
At Badrinath, Lord Vishnu became visible to Shankara and he told him that his statue/idol in the Alakananda River should be made out and a temple should be constructed for it. This temple is known as Badrinarayan Temple which is the most religious temple.
Significance of Adi Shankracharya Jayanti :
Shankaracharya taught everyone the belief of Advaita Vedanta.
He also studied and taught the main principles of the Brahma Sutras, Bhagavad Gita and the Upanishads
Shankaracharya condemned the focus on strict rituals and ceremonies, which some schools of Hinduism pardoned
Though he approved the immensity of the Vedas, he explained them differently and denounced some of its very old ritualistic practices; which he thought as being regressive
People are very much influenced by Shankaracharya's teachings
He moved and travelled across the country to teach and make people aware of his conviction and revive Hinduism
Shankaracharya was a great devotee of Lord Shiva
His most famous literary work is the Bhaja Govindam