In the context of ETL (Extract, Transform, Load) systems in general, a data source, broadly defined, refers to any location or system that provides data that can be extracted and transformed. This includes enterprise data stores from specific ERP, CRM, and other business systems.
In ETL+ data sources are shown on ETL+'s Source Objects (formerly ETL Source) panel. In the context of ETL+ a data source represents the combination of a Source Type (a type of connection to a data store system such as MS SQL Server, HubSpot ODBC, or OData) with a Source Container (a specific data source repository such as a specific database on MS SQL Server, a Google Sheets spreadsheet, or the data behind an OData URL, or a NetSuite ODBC DSN.
may refer to the databases, files, etc shown in the ETL Source panel.
DataSelf provides pages with information on connecting to specific enterprise data stores as well as pages on connecting to ODBC, relational databases, 'flat files” (CSV, JSON), and Excel files. DataSelf has templates (pre-defined/out-of-the-box mappings) for ETL+ to extract, transform and load data into data warehouses.
Technically, for ETL (Extract, Transform, Load) systems, "data sources" refer to the origin of the data that is being extracted and transformed before it is loaded into a target database or data warehouse.
Data Source has other meanings when used in the context of Tableau and Tableau reports.