A Cyclic Redundancy Check (CRC) is an error-detecting code used to ensure the integrity of data during transmission or storage. It works by applying a mathematical algorithm to a block of data, generating a short, fixed-size binary value called a checksum. This checksum is sent along with the data, allowing the receiver to verify if the data has been altered or corrupted. When the data is received, the same CRC algorithm is applied to the received data. If the calculated checksum matches the one sent, the data is considered intact. If not, it indicates an error, prompting a retransmission or correction of the data.