Projects can be broken down into several phases. The culmination of these phases is known as the project lifecycle. During each of these phases there will be some output of your work to show that the project is going forward. These outputs are known as deliverables. PMBOK defines a deliverable as a "tangible, verifiable work product." This could include blueprints, designs, or a prototype. It could also include all the project-related reports, such as status reports, communication plans, and reviews at the end of each phase of the project.
PMBOK refers to these phase-end reviews as phase exits, stage gates, or kill points, and they involve lessons learned, analysis, and providing feedback to stakeholders, team members, and other people associated with the project.
A project lifecycle includes everything from the beginning to the end of a project. It has several characteristics, which are summarized in the PMBOK. These characteristics are discussed in the following paragraphs.
Cost and staffing levels tend to increase as you begin a project, and they progress toward the end of the project and then decrease quickly as the project is completed. Consequently, the levels of activity increase gradually during the initiation phase, continue to escalate during the planning phase, and peak during the execution phase. The levels of activity then decrease as you approach the project closeout. This is diagrammed in Figure 2-1 on page 13 of the PMBOK.
The risk of project failure is highest at the beginning and gradually decreases over time as the probability of success increases. This is because the uncertainty of project success is the highest at the beginning of the project. This uncertainty decreases as you proceed through the project and achieve milestones and provide key deliverables. As more milestones are achieved and deliverables provided, the confidence level increases and the success of the project becomes more inevitable.
Stakeholder impact is highest in the beginning of a project and decreases as the project proceeds. Project stakeholders are individuals and organizations actively involved in the project and have some type of vested interest. Their impact is highest at the beginning because the project is still being planned and not everyone has bought in to the project plan and set a definitive path for the project.