Cyclical Redundancy Check checksum file
CRC is a file extension for a Cyclical Redundancy Check checksum file used to verify the data integrity of another file. CRC is a popular technique for checking data integrity as it has excellent error detection abilities, uses little resources and is easily used.
Learn more about CRC files:
Wikipedia has an entry on CRC.
Carrie Higbie discusses CRC errors and other common network errors.
Search for answers to CRC-related questions at IT Knowledge Exchange.