RAR stands for Roshal ARchive. It is a proprietary archive file format that supports data compression, error recovery, and file spanning. It was developed by a Russian software engineer, Eugene Roshal (the first letter of his surname contributing to the name of the archive format), and is currently licensed by win.rar GmbH.
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 split into many smaller files (a "multi-volume archive"), the smaller files used the extensions .rar, .r00, .r01, .r02 etc.
How To Extract Multiple Split Archive Files
Rar is capable of making a large rar archive file into lots of smaller files, for safer transport. This makes no difference to the extracting process. To join-and-extract them, just run the e option as normal.
rar e filename.whatever.rar
This will join all the files together then extract the original file. This will be listed on the last line.