The spells used to reanimate a human body are much more complex than those used, for instance, to make inanimate objects fly. The Inferius may be cursed to respond lethally if disturbed, to kill indiscriminately, and to undertake perilous jobs for its master. Its limitations are, however, obvious; it has no will and no brain of its own, and will not be able to think its way out of unforeseen trouble. As a warrior or guardian with no regard for its own safety, however, it has many uses.

The Inferi whom Harry and Dumbledore encounter in the depths of the lake in Harry Potter and the Half-Blood Prince were, when alive, mostly vagrant, homeless Muggles whom Voldemort had murdered for the purpose during his first rise to power, although some were the earthly remains of wizards or witches who 'disappeared' without explanation.

J.K. Rowling: Inferi have much in common with zombies, which are mentioned as separate creatures within Harry's world. I had several good reasons for not wishing to call the guardians of the locket Horcrux 'zombies'.

While zombies of the Vodou tradition can be nothing more than reanimated corpses, a separate but related tradition has it that the sorcerer uses their souls, or part of their souls, to sustain himself. This conflicted with my Horcrux story, and I did not wish to suggest that Voldemort had any more use for his Inferi than as guards of his Horcrux.