Full Idea
Philosophers' zombies (invented by Robert Kirk) differ from the zombies of folklore; they are intended to make clear the idea that consciousness is an addition of being, something 'over and above' the physical world.
Clarification
A zombie is a human that lacks consciousness
Gist of Idea
Philosophers' zombies aim to show consciousness is over and above the physical world
Source
John Heil (From an Ontological Point of View [2003], 20.1 n1)
Book Reference
Heil,John: 'From an Ontological Point of View' [OUP 2005], p.241
A Reaction
The famous defender of zombies is David Chalmers. You can't believe in zombies if you believe (as I do) that 'the physical entails the mental'. Could there be redness without something that is red? If consciousness is extra, what is conscious?