Checksum is often used in Bitcoin when generating public key, address. Checksum is a simple method for error-checking data .
In Bitcoin blockchain the checksum is generated by running SHA256 function two times in a row.
Important note: need to use sha256 in binary mode for binary data.
Bitcoin checksum on Linux Bash: sha256sum
This is an example used on learnmeabitcoin  and this bash analogue gives the same result: