the purpose of the hotlinking is to allow referencing of a file in another file when there is for example repetition...
so the interior design of a room or a flat or even a whole house, replicated several times in another file (the host file) which would be a flat, a building or a whole site in the examples stated.
the idea being that if you change the module and then updated it in the host file, all instances could be updated in one step, rather that doings multiple copies of the same thing in one file and the having to revise each one.
i hope this makes sense to you and can help you understand the concept of hotlinking.