RAR is a type of file compression, a sibling to Zip files. Most Zip utilities -- unZip programs, such as WinZip -- can handle RAR. If yours does not, I use a file un-compressor, FilZip, available free at http://www.filzip.com/en/index.html
I think it handles all versions of RAR, but might be wrong. I haven't actually seen a RAR file in a long time.
FilZip is not as friendly as WinZip, but you can open compressed archives and drag-and-drop the files you want onto open Exporer folders.