A host body is a body used, infected or possessed by another creature, usually one who was incorporeal or very small.
GeneralWhen a foreign entity like that of a Symbiote, Body Snatcher, Puppeteer, Parasite, or even a Hacker Body Snatcher, Puppeteer Parasite, or even a Hacker (when regarding machines like robots and computers) enters/outright hijacks a body, the possessed subject becomes what is usually called: the Host. The basic purpose of the host varies on what the point was for it to have been hijacked in the first place. Sometimes it's used as a disguise, other times it's used as a decoy and destraction, even simply being used as a weapon and piece of armor that the possessor uses to cause sheer chaos and destruction.
In The Host
An alien race called, souls, use their host bodies to survive. These creatures can't stay away from their host bodies for a long time (except in the planet Origin) and have to die without them.
They are inserted inside a healthy creature's body and become the one cotrolling it.