The term Project Plan is often loosely used. In most of our project engagements, we often have to clarify that Project Plan is not just a Microsoft Project Plan. A project plan is a document and is an output of the project planning process. Developing a project plan encompasses everything that is done during project planning.
Some elements that are contained in the project plan are:
Having a documented Project Plan is essential. If your project does not have one and you are the Project Manager, make one. It will prove useful to you. 