This process aims to lay down foundations to achieve a successful project. It tries to do this by ensuring everybody involved is clear on what the project intends to achieve, why it is needed, how it is to be achieved and what their responsibilities are.
This process allows the project board to decide whether or not the project is aligned enough with organisational or programme objectives to authorise the project to continue. If may be risky to allow a project to continue if it is not fully understood (risk of loosing resources like time/money/people).
All the activities within the process need to be taken for further consideration if the relationship between customer and supplier is commerical because they may have different understandings as to why the project needs to be undertaken.
The project manager will be creating the management products required for the level of control required by the project board. This should have been agreed as part of the initiation stage plan and describes the way the project board will review and approve the management products (two extremes are one at a time or all at once).