Yes, although it is optional. URL mapping allows portal administrators to create a different URL and map it to portal pages.
On providing a directory path for a file system collection, URL mapping can be optionally set for each directory.
For example, C:\testfolder can be mapped to http://www.examplesite.com so that even though SearchBlox indexes the content from the file system when a user clicks on the search result, the web document is served from the webserver. The child path would be automatically mapped to the URL.
To learn about File System Collection read: File System Collection in SearchBlox