The Data Flow task encapsulates the data flow engine that moves data between sources and destinations, and lets the user transform, clean, and modify data as it is moved. Addition of a Data Flow task to a package control flow makes it possible for the package to extract, transform, and load data.
A data flow consists of at least one data flow component, but it is typically a set of connected data flow components: sources that extract data; transformations that modify, route, or summarize data; and destinations that load data.
At run time, the Data Flow task builds an execution plan from the data flow, and the data flow engine executes the plan. You can create a Data Flow task that has no data flow, but the task executes only if it includes at least one data flow.
To bulk insert data from text files into a SQL Server database, you can use the Bulk Insert task instead of a Data Flow task and a data flow. However, the Bulk Insert task cannot transform data.