Functional Requirements for Bibliographic Records (FRBR) presents a complex conceptual model. Because of this, it is not easy for everyone to understand. The purpose of this paper is to make some of the more difficult aspects of the FRBR model, in particular the Group 1 entities work, expression, manifestation, and item, easier to understand by placing FRBR in the context of what it is: a conceptual entity-relationship model. To this end, a definition of the term �model� is presented, a variety of types and functions of models are introduced, conceptual models are discussed in detail, modeling an abstraction is explained, and different ways of interpreting FRBR are suggested. Various models used in the history of cataloging are introduced to place FRBR in the context of the historical development of document models.