Zombies are creatures who's brains have been taken over by a disease which is not named. The disease was caused by stupid muggles tampering with science.

Basic Rules When Dealing With Zombies

Rule 1: Do not attempt to talk to a zombie if you see one.

Rule 2: Immediately dispose of a zombie in any way necessary.

Rule 3: Spells will only aggregate zombies further, use conventional weaponry.

Rule 4: If infected you only have hours to live before dying admit to the closest hospital.