According to the Advaita Vedānta as propounded by Śaṅkara (A. D. 788-820) the ultimate Reality is one only, the one without a second—ekam eva advitīyam brahma. But that we perceive this world of multiplicity, is a fact of experience. Śaṅkara attributes this to māyā or avidyā or ajñāna (illusion or nescience or ignorance). This māyā/ avidyā covers this Truth or Brahman and makes it appear as something else which it really is not, viz., the world. For instance, the semidarkness of twilight covers up the real nature of a rope and the semilight projects it as a snake. The power of māyā/avidyā to veil the truth is called ‘āvaraṇaśakti’ and its power to project it as something else, is called ‘vikṣepaśakti.’
Just as bright light destroys the illusory perception of the snake in the rope, even so jñāna, knowledge or direct experience of the Truth (Brahman/Ātman) will destroy this māyā/avidyā.