Whilst Running R3cover I Get A Disk Read Error

I get a disk read error when attempting to scan my hard drive, what does this mean?

Disk Read errors are bad sectors or areas of degraded media that your computer cannot read from your hard disk.  R3Cover software can only scan readable information from a drive.  R3Cover will in most cases continue to scan the hard drive or device upon encountering a read error, however, it is recommended that you halt the scan at that point and seek professional Data Recovery assistance.