http://en.wikipedia.org/wiki/RARQUOTE
In computing, RAR is a proprietary archive file format that supports data compression, error recovery, and file spanning.[1] It was developed by a Russian software engineer, Eugene Roshal (hence the name RAR: Roshal ARchive; RAR is also known as a backronym for 'Rational And Reliable'), and is currently licensed by win.rar GmbH.[2]
The filename extension used by RAR is .rar for the data volume set and .rev for the recovery volume set. In previous versions, if a RAR-archive was broken into many smaller files (a "multi-volume archive"), then the smaller files used the extensions .rar, .r00, .r01, .r02 etc.
IMO, the best program to handle RAR (and pretty much every other archive) is 7zip, as per
http://en.wikipedia.org/wiki/7-ZipIts free and its awesome. Winzip, Winrar and WinAce are all buckets of steaming horse shit compared to the fine top soil that is 7z.