It is a permanent act performed with a spirit or a spell.  In the case of a spirit it is a mutual agreement transacted between a conjurer/practitioner & a spirit for the spirit to be associated with an object or person.  When a spirit or enchantment is bound to someone or something that binding act is a permanent placeholder for the spirit or spell. When a spirit is bound to a person or bound to an object that is a permanent act that creates a haven for the spirit. The vessel, be it person or object, is the physical realm binding site which remains unless purposefully dissolved by the person.