Advaita Vedanta (Advaita Vedānta) is a sub-school of the Vedānta (literally, end or the goal of the Vedas, Sanskrit) school of Hindu philosophy, the other major sub-schools being Dvaita and Viśishṭādvaita. Advaita (literally, non-duality) is often called a monistic system of thought. The word “Advaita” essentially refers to the identity of the Self (Atman) and the Whole (Brahman). The key source texts for all schools of Vedānta are the Prasthanatrayi— the canonical texts consisting of the Upanishads, the Bhagavad Gita and the Brahma Sutras.
Adi Shankara, 788–820 CE, was the first in the tradition of Advaita Vedanta who consolidated the Advaita Vedanta siddhānta (system). He wrote commentaries on the Prasthana Trayi. A famous quote from Vivekacūdāmani, one of his Prakarana granthas (philosophical treatises) that succintly summarises his philosophy is:
Brahma satyam jagat mithyā, jīvo brahmaiva nāparah
Brahman is the only truth, the world is unreal, and there is ultimately no difference between Brahman and individual self.