An ihost is an “internal” host, a SimulationHost process running on a server at MakenaTechnologies. This is as opposed to a uhost (“user” host), a SimulationHost process running in the ThereClient on a member’s computer.
Alternative definition from a forum post:
An ihost is an “I” host, a simulation server at MakenaTechnologies. Different ihosts simulate different sectors of PlanetThereia. This is as opposed to the uhost (“you” host), which is the client machine where the ThereClient runs. “I” and “you” are therefore server-centric terms.