There are several purposes of a Service Transition. These purposes include: ensuring that a service can be managed, operated, and supported; providing quality knowledge of Change, Release and Deployment Management; and the planning and management of the capacity and resource requirements to manage a release.
The Service Transition comes down to building and deploying IT services which does encompass all of the aforementioned. It does not, however, include training and certification in project management. This is generally done before work commences and services are deployed.