BW is SAP’s Data Warehouse offering. BW replaces selected R/3 information systems over a period of time. End to End open DW Solution – all in one package comprising data extractors, administrator workbench, OLAP engine and a graphical user interface. It is pre-configured for the needs of the business users with delivered Cubes, reports, templates.

Front-End (BEx Analyzer)- provides access to the data via internet, intranets or extranets.  Presentation backend is MS Excel. Open solution that allows data to be loaded from practically any source or system, including 3rd party systems and legacy applications. You can also use 3rd party extracting / reporting tools via BAPI’s. BW changes the focus from Build to Buy and it provides faster integration and implementation.

Understand a lot more about General, Architecture and Reporting in this manual on BIW Overview (611)