ETL (Extract-Transform-Load) tools are part of Business Intelligence systems. They allow connecting the data from different sources using dedicated drivers. BI tools can be connected with different IT systems (e.g., ERP, CRM), databases, and external files (e.g., Excel and CSV). When it is necessary to integrate the data from sources that don't have predefined drivers, it is possible to use ODBC or OLE DB interface.
ETL tool selection is an essential part of Business Intelligence system designing. It is worth it to benefit from specialists' experience who have done a lot of BI implementations and know this type of tool.