A checksum is a value calculated from a data set to verify its integrity. It acts like a digital fingerprint, allowing users to check if the data has been altered or corrupted during transmission or storage. Commonly used in computer networks and file transfers, checksums help ensure that the received data matches the original. When data is sent over the internet, a checksum is generated and sent along with it. The recipient can then calculate the checksum of the received data and compare it to the original. If the two checksums match, the data is likely intact; if not, it may have been compromised or corrupted during the process.