In the PRINCE2 methodology, the 'project mandate' is the term used for initial documentation that triggers the start of a project, typically provided by corporate or program management. It can often come in the form of a request for proposal received by an external supplier, setting out the initial definition of the project and what it aims to achieve, which then leads to more detailed project definitions in the 'starting up a project' process.
PRINCE2 7 Foundation resources on project initiation documentation.

When executing a Work Package, the Team Plan is used to organize and control the work. The Team Plan is derived from the Stage Plan and provides detailed allocations and explanations of how the team will deliver the work package assigned to them. It focuses specifically on the tasks and resources at the team level, detailing the schedule and resources needed to complete the work.
(PRINCE2 7 Foundation Handbook, AXELOS)