scheduling is the process of determining when project activities will take place depending on defined durations and precedent activities. Schedule constraints specify when an activity should start or end based on duration, predecessors, external predecessor relationships, resource availability, or target dates.
Determining the start and stop time of each activity and task in the project, taking into account the precedence relations among tasks, the dependencies of tasks on external events, the required milestone dates, and the resources available
Setting the project plan dates for executing project work and achieving project milestones. See section 6.5.2 of the PMBOK.