What is a Project Plan?
“A project plan, according to the Project Management Body of Knowledge (PMBOK), is a formal, approved document used to guide both project execution and project control.”
In Prince 2 the Project Plan is the top level of plans. The Project Manager creates the Project Plan at the start of the Project. It shows the work that needs to be done from the point after the initiation stage to the end of the project and provides the Business Case with the planned costs and time. It describes the main products that are to be delivered in the project and shows broadly the activities and resources that are needed to deliver them. It should indicate how the project will be divided into various management stages.
After the Project Manager creates the Project Plan the Project Board reviews its contents and decides whether to authorize the project. They do this review in their Directing a Project process.
Once the project is active, the Project Board uses the Project Plan (once again during Directing a Project) to track and monitor the progress of the project. It provides an appropriate high level of detail for the members of the Project Board, because, given their seniority in the project, it is unlikely they will want to get involved in the day-to-day details.
At the end of each stage during Managing a Stage Boundary, the Project Manager updates the Project Plan with high-level details of what occurred in that stage as well as any new high-level details for the subsequent stages that are now known.