The idea of a project phase is very handy to grasp for the project team manager and or the project management team because it is one of the many project management concepts and tools that allow the project management team and or the project management team leader to effectively manage the project timeline in a logical and concise manner. Specifically speaking, the project phase refers to the grouping of a number of related project activities into one specific project phase. The conclusion of a specific project phase usually results in the completion of a particular major deliverable related to the project. These project phases are typically completed in a sequential manner, however in some cases depending on the situation there may be some sort of an overlap. For the purposes of organizational ease, it is also possible so subdivide phases into subphases and then even further into components. Overall, the sum total of all project phases will ultimately make up the project life cycle.
This term is defined in the 3rd and the 4th edition of the PMBOK.