From Wikipedia: A Guide to the Project Management Body of Knowledge:
A Guide to the Project Management Body of Knowledge (PMBOK Guide) is a project management guide, and an internationally recognized standard, that provides the fundamentals of project management as they apply to a wide range of projects, including construction, software, engineering, automotive, etc.
A Guide to the Project Management Body of Knowledge (PMBOK Guide) was first published by the Project Management Institute (PMI) as a white paper in 1987 in an attempt to document and standardize generally accepted project management information and practices. The first edition was published in 1996 followed by the second edition in 2000.
In 2004 the PMBOK Guide - Third Edition was published with major changes from the first edition. The English-language PMBOK Guide - Fourth Edition was released on December 31, 2008.