Adi Shankara (788 CE - 820 CE), also known as Sankara Bhagavadpada and Adi Sankaracarya was an Indian Guru from Kalady of present day Kerala who consolidated the doctrine of Advaita Vedanta. His teachings are based on the unity of the Atman and Brahman - non-dual Brahman, in which Brahman is viewed as Nirguna Brahman, Brahman without attributes.
Shankara traveled across India and other parts of South Asia to propagate his philosophy through discourses and debates with other thinkers. He is reputed to have founded four maths (“monasteries”), which helped in the historical development, revival and spread of Advaita Vedanta. Adi Shankara is believed to be the organizer of the Dashanami monastic order and the founder of the Shanmata tradition of worship.
His works in Sanskrit concern themselves with establishing the doctrine of Advaita (nondualism). He also established the importance of monastic life as sanctioned in the Upanishads and Brahma Sutra, in a time when the Mimamsa school established strict ritualism and ridiculed monasticism. Shankara represented his works as elaborating on ideas found in the Upanishads, and he wrote copious commentaries on the Vedic canon (Brahma Sutra, principal upanishads and Bhagavad Gita) in support of his thesis.