The SSIS control flow defines the workflow for that package. It determines the order in which tasks and containers will execute. In certain condition the tasks will run only when a set of defined conditions are met. Precedence constraints link the individual tasks together and determine how the workflow moves from one task to another. Precedence constraints are only used with Control flow Tasks and not with Data Flow. The connections between objects within the control flow are done by precedence constraints and in data flow are data path.