A host body is a body used, infected or possessed by another creature, usually one who was incorporeal or very small.
General[]
When a foreign entity like that of a Symbiote, Body Snatcher, Puppeteer Parasite, or even a Hacker
A soul named Wanderer using her host body of a human
(when regarding machines like robots and computers) enters/outright hijacks a body, the possessed subject becomes what is usually called a 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 on the Origin ) and have to die without them.
They are inserted inside a healthy creature's body and become the one cotrolling it.