rar files

I don't believe the Mac operating system has a built-in tool to handle .RAR files. It does for .ZIP files.

See this https://en.wikipedia.org/wiki/RAR_(file_format) for some background on RAR files.

I use MacPar Deluxe to process RAR files. See - https://gp.home.xs4all.nl/Site/MacPAR_deLuxe.html

PAR files are related to RAR files as the name might give away. PAR files are used to help 'repair' corrupt RAR files. You might download a very large file that has been converted in to multiple RAR files. If one of those RAR files is damaged or missing, then a PAR or multiple PAR files can reconstruct the problem RAR files.

MacPar Deluxe now supports the new RAR version 5 format as well.

A rar filr is an archived compressed file. Check the app store for apps that can unzip rar files.

As Bob says, but the OS should unpack them, they should be safe to unpack.