Although the terms “plan” and “schedule” are at times used interchangeably, they are in fact very different. A complete project plan contains a project schedule - but it also includes much more than that (e.g., risk management, quality management, human resource management, and procurement). These differences have implications for the layman as well as the experienced project manager and have implications for successful project management practice. Additionally, the contents of the project plan have evolved over time as versions of the project management body of knowledge (PMBOK) were updated.