Because many project managers have never completed activities in this phase (never completed a project charter, never signed a contract, and so on), let's quickly review why PMI considers project initiation an important process.
Initiation is the first step in the project management process, and it is the first step in the scope-management process. It authorizes (formally) a project to begin and links a project to the work and to the strategic objectives of the organization.
Be sure to understand that the Initiation step can occur more than once in a project. The Initiation process is also performed at the end of each project phase to get authorization to continue the project. A common term for this point is a go/no-go decision.