Creates a data source containing media libraries, which can then be provided to listing web parts (such as a Basic repeater) in order to be displayed.

Please note that this web part creates a data source containing the libraries that store media files. If you wish to retrieve the actual file content of a library, the Media files data source web part should be used instead. 

Help URL: http://devnet.kentico.com/docs/webparts/index.html?MediaLibraryDataSource_overview.htm