Source : WordNet®

file server
     n : (computer science) a digital computer that provides
         workstations on a network with controlled access to
         shared resources

Source : Free On-Line Dictionary of Computing

file server
     
        Hardware and software that together provide file-handling and
        storage functions for multiple users on a {local area
        network}.  The most common choices for file server software
        are {Sun Microsystems}' {Network File System} for {Unix} and
        {Novell Netware} for {IBM PC} compatibles.  There is also a
        version of NFS for PCs called {PC-NFS}.  Storing files on a
        file server saves having multiple copies stored on individual
        computers, thus economising on disk space and also makes
        administrating and updating the files easier.