A host is a physical entity occupied by one or more persons not genetically linked to the body. (commonly called a "Host" for short, but not to be confused with the psychologist's term 'host' for the base personality in a multiple). The term as used in the multiple community is derived from the idea that a symbiotic relationship has a "host" and a "symbiant" entity AND from the idea of a "host" being a group as in "The Heavenly Host."
Otherkin Host?: a Host situation where one or more of the entities in the body are non-human in nature.
Types of residents that might be found in hosting situations:
Walk-In - Someone who joins the body well after birth...
Analog - same person raised in a different reality, dimension or universe - for example, (Buffy: The Vampire Slayer reference) Evil Willow vs. the normal "Willow" or (comic book reference) Bizzaro vs. Superman. A good example of an "alternate reality," from what I understand, is every situation found in Sliders episodes, Quantam Leap, and timestream issues found in Star Trek episodes.
Channeled - person has a hotline into your head...or has found out your mental phone number...not necessarily a resident, but is more like a temporary guest. Temporary guests might decide to stay for a long duration, or even permanently, but their source still might be that they were initially channeled.