PMBOK or Project Management body of knowledge is a manual or guide published by PMI (Project Management Institute) to assist practicing project managers. This guide aims to provide processes by following which, likelihood of a success of project increases.
This manual lists processes in two classifications, by knowledge areas and process groups. Currently, version 4 is the followed guide. Overall, this version talks about 42 processes.
This is a comprehensive guide which provides a close insight to Project Management. A must for all project managers and bible for PMP aspirants.