If you are aspiring to take your PMP Certification, you should know that if there is one single page that you really have to memorize, that is the page 42.
That page of PMBOK shows the mapping of the Project Management Process Groups and Knowledge Areas.
There are 5 Process Groups that have clear dependencies and are followed in sequence.
INITIATING process group (when the project is officially started)
PLANNING process group (remember the project plan? you do it here together with your subsidiary plans)
EXECUTING process group (this is it, start working on what was in your plan)
MONITORING and CONTROLLING process group (you make a plan because you plan to succeed, and this is where you cross check if you are on the right track based on your plan)
CLOSING process group (when you think your project is completed, think again before you officially closed)
Note: The 5 Process groups are not Phases. An individual phase (it could be better seen in WBS) could also be using the 5 process groups.
GMWalterhouse 