Project planning involves breaking down work into tasks assigned to team members, anticipating problems, and creating a project plan. The plan is used to communicate work and assess progress. Planning occurs at proposal, startup, and periodically throughout the project. At startup, more details are known and a plan is created for resource allocation. During development, the plan is regularly revised based on new information and experience. Agile planning uses iterative increments and flexible plans that can accommodate changing priorities and requirements.