These are files containing checksum info. This technique is widely used to validate and recover binary files exchanged over a network.
If you upload and download binary files to and from newsgroups, you can use this to generate a set of PAR files. If you miss one or more of the subject files when downloading, the program can restore the missing files.
If the PAR set contains a RAR archive, it is automatically unpacked after the PAR verification is complete.
Requires Mac OS X 10.1 or later