RAR 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. RAR stands for Roshal Archive and the RAR software is licensed by win. rar GmbH.
Source: Wikipedia
How to Install RAR
macOS
$ brew install unrar
How to Uncompress a RAR File
$ unrar x <filename>
Source(s): superuser