Par and Par2 files are used to repair damaged files based on their binary pattern. The name Par comes from Parity. These files can be used to reconstruct damaged files or ones that are missing from a parity set. For example, if you have downloaded an archive that was split into 47 files but one of them is missing, you could simply download a PAR file for that archive. Once you have the PAR file, you can use a PAR program to reconstruct the missing file.