The Data Sources tab lists the physical data sources to which you have created connections. You can also launch the Connection Wizard from this tab, where you create data source connections. Other tasks that you can perform from the Data Sources tab:
View sample data from a selected table in a data source
Show the “friendly names” of tables in a Microsoft SQL Server data source
Refresh the data sources list
Introspection, an analysis of the data source connection to identify possible hierarchies
Incrementally update an existing data source
Create user-defined tables
See Data Source Connections for more information.