:.prop refers to

This property states that a certain property can / should be used to connect to an instances of the specified class.

Example: A property named 'lived at' might be useful to describe instances of a class named Person. And it will typically refer to an instance of class Location

So, in Property:Lived at you would write {{describes class|Person}} {{refers to class|Location}}.

Note that we use a template called refers to class rather than a direct property assignment.

This property is assigned by .prop assigned by::Template:.prop refers to