Search Providers 
Search providers are back-end systems or services that are connected to the Enterprise Search appliance to integrate the search objects that they contain in searches conducted with Enterprise Search.
Enterprise Search federates the search results from different search providers. Search providers are classified as follows:
Search service providers:
These are systems and services that return search results to Enterprise Search using their own search technology. Here, the query request is delegated from Enterprise Search to the search service providers.
These include:
SAP systems, such as KM and SAP ERP 6.0 (ERP 2005), that use their own search technology, for example, Search Engine Service (SES)
Web Services
File servers that use their own search engine
Search Data Providers
These are systems that provide searchable data that is extracted, indexed, and searched using Enterprise Search technology.
These include:
SAP R/3 release 4.6C or 4.7 (SAP R/3 Enterprise)
File servers based on Windows 2000/2003 Server that do not have or use their own search engine
Web servers based on Windows 2000/2003 Server that do not have or use their own search engine