This is where you define what needs to be accomplished and how. The activities of this phase includes defining the project objective, scope, governance structure, schedule, deliverables, challenges and critical success factors. This information is usually documented in the project charter.
NOTE: Business justification should happen before the initiation phase.
Once the project charter is approved you can start working on the detailed planning activities. The outcome of the planning phase is a detailed project plan and the project schedule.
Project execution involves coordinating people and resources, monitoring the project progress (planned vs. actual), conducting project team meetings and steering committee meetings, and evaluating and mitigating risks.In terms of ITIL this is where you define, deploy and operate (pilot) the ITIL processes.
Here you evaluate if the project objectives were met, what went right and what went wrong, document lessons learnt, celebrate etc.