Par2 Files are common on the Usenet today.They are not that common on the Internet in general and I can’t think of a location where I encountered them except for the Usenet. Par2 Files can be used to repair broken archives. That is the basic explanation of course, the technical is a little bit more complicated. Lets use a example to make it clearer. Let us assume that you have downloaded a number of rar files (.rar, r01, r02 and so on) that can be unpacked to create the file test.avi which has a size of 700 Megabytes.
Let us further assume that some of the rar files have been uploaded incompletely to the Usenet which happens from time to time. It would not be possible to extract test.avi because of the broken files in the archive. Par2 Files are fixers. They analyze the blocks of each rar archive and post back if it is complete, incomplete or missing. Every Par2 file can be used to fix a certain number of blocks that corresponds to the amount of blocks of the rar files.