PMBOK is 'Project Management Body of Knowledge', and was first published in 1987 by the PMI (Project Management Institute). Like other methods, it is occasionally revised, the most recent publication being in 2004.

The PMBOK guide defines 5 main processes:
Initiating
Planning
Executing
Controlling
Closing

And 9 'knowledge areas':
Project Scope Management
Project Integration Management
Project Time Management
Project Cost Management
Project Quality Management
Project HR Management
Project Risk Management
Project Procurement Management
Project Communications Management