What type of tenancy allows for indefinite occupation, where either party can terminate at any time?

The type of tenancy that allows for indefinite occupation, where either party can terminate at any time, is indeed a tenancy at will. This arrangement is characterized by its flexibility; it does not have a fixed or definite term, meaning that either the landlord or the tenant can terminate the tenancy without providing a long notice period, as long as it complies with local laws regarding notice.

This is distinct from other types of tenancies, which have specific terms and conditions regarding duration and termination. For example, tenancy in common, joint tenancy, and tenancy by the entirety involve shared ownership arrangements typically concerning ownership interests in property, and they do not inherently provide the same level of flexibility regarding occupation or termination as a tenancy at will.