Peter F. Drucker distinguishes between management, which is doing things right, and leadership, which is doing the right things. Project management consists of three phases: project planning, scheduling, and project control. The project planning phase involves developing a work breakdown structure, estimating costs and time, and allocating resources. In the scheduling phase, activities are identified and their durations and interrelationships are estimated to develop a network diagram and calculate floats and critical paths. The project control phase involves evaluating actual progress against the plan and revising uncompleted work if needed through reallocating resources.