Errors in reading an optical disc are always present, and CD players have some form of error correction built in. Error correction insures that you have a bit perfect rip to your hard drive.
Apple says "use error correction if you experience problems with the audio quality...", but you should do it as a standard practice. They also say that it may reduce the speed of importing, but that is only noticeable in older computers.
Error correction can often enable importing from CDs that were unplayable, depending on the severity of the damage. Many people have ripped discs that were skipping or misreading, and using error correction, burned the ripped files back to a CD-R disc and had a playable CD.
Steve