Checksum Code is a calculated value that is used to determine the integrity of data. Checksum serves as a unique identifier for the data (a file, a text string, or a hexadecimal string) or as a method of detecting unwarranted changes to the data.
Checksum codes are typically integrated into MRZ lines in ID documents, mostly Passports and other travel documents but also some ID cards and driver’s licences, where it serves as a logical method for detecting forgery or counterfeiting attempts.
Checksum is checked using a formula that is in practice more effectively checked using technology than manually
Ref.: http://www.geeksengine.com/article/checksum.html