The concept of the philosophical zombie is one that was popularised by David Chalmers and discussed at length in Chalmers 1996. Since then the idea has been the subject of much debate with numerous classes of zombie and zombie world having been proposed. There is considerable disagreement as whether zombies are possible/conceivable and what it would mean if they were.

A philosophical zombie is the same as any other person except they lack phenomenal consciousness and its associated qualia. Although not explicitly part of the definition, it seems reasonable that such zombies would also lack free will.

Much of the debate about philosophical zombies centres around how closely they need to resemble their qualia-based counterparts and whether they are conceivable and/or possible.

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References:

Chambers, David J. The Conscious Mind (OUP, 1996)