A host is the headmate who is most active, most responsible for day-to-day activities, or otherwise is fronting most often.
Not all systems have hosts, and some may have a rotating team for the role. In addition, some do not like the term "host", and choose to use alternatives; specifically, outernaut.
Host is oftentimes confused for "core", because, in some systems, one headmate is both. The former can be any headmate of any origin, while the latter refers to a body's native personality; both may or may not exist in a system.
A co-host (or perinaut) is exactly what it sounds like: a headmate that, with others, shares the hosting role.
It is also not to be confused with main.
Depending on the type of system, soulbonder and tulpamancer may also be used.
Host may align with one's singletsona.