How is checksum used?
To prevent or notify of data corruption.
When a system is storing some data, it computes a checksum of the data and stores the checksum with the data. When a client retrieves data, it verifies that the data it received from the server matches the checksum stored.
What is a checksum?
The result of a cryptographic hash function like MD5, SHA-1, SHA-256, or SHA-512.