A checksum is a small piece of data derived from a larger set of data, used to verify the integrity of that data. It is created by applying a mathematical algorithm to the original data, producing a unique value. When the data is transmitted or stored, the checksum can be recalculated and compared to the original to ensure that no errors occurred during the process. Checksums are commonly used in computer science, especially in data transmission and storage systems. They help detect errors in files, such as those found in network communications or data storage devices. If the checksums do not match, it indicates that the data may have been corrupted or altered.