"The BIBFRAME Model is a conceptual/practical model that balances the needs of those recording detailed bibliographic description, the needs of those describing other cultural materials, and those who do not require such a detailed level of description. There are four high-level classes, or entitities, in the BIBFRAME Model: BIBFRAME Work; BIBFRAME Instance; BIBFRAME Authority; BIBFRAME Annotation. BIBFRAME Work identifies the conceptual essence of something; a BIBFRAME Instance reflects the material embodiment of a Work; a BIBFRAME Authority identifies a thing or concept associated with a BIBFRAME Work or Instance; and a BIBFRAME Annotation provides a new way to expand the description of a BIBFRAME Work, Instance, or Authority. You can read more about the BIBFRAME Model here.
The BIBFRAME Vocabulary is the key to the description of resources. Like the MARC format has a defined set of elements and attributes, the BIBFRAME Vocabulary has a defined set of classes and properties. A class identifies a type of BIBFRAME resource (much like a MARC field might bundle a single concept); properties serve a means to further describe a BIBFRAME resource (much like MARC subfields more specifically identify aspects of the concept)."