Maya means illusory or unreal and is a philosophical concept of a school of Hindu philosophy [wiki]Advaita[/wiki] of the wider school [wiki]Vedanta[/wiki] It posits that all of phenomental reality is ultimately unreal or a sensory distortion. It is derived from the etymology of ma+ya, where ‘ma’ means source, producer and ‘ya’ means that which moves or goes. Thus maya is the source of all transient and active phenomena and because all phenomena is transient it is ultimately unreal because it lacks beingness; one moment it is there, the other moment it is not. In contrast to maya is the concept of [wiki]Brahman[/wiki] which is unchanging, eternal and absolute reality.
Maya is described as another aspect of brahman in advaita, somewhat like a mirror image and as it is an image it is an unreal representation of brahman. In the Bhagvad Gita, Lord Krishna calls maya his energy which emanates from him and creates the phenomenal world.
Maya is similar to the Samkhya concept of [wiki]prakriti[/wiki]