Since Windows and macOS do not natively support extracting .rar files (they typically only handle .zip ), you will need to install a third-party application.
A free, open-source alternative that supports a wide variety of formats, including RAR. 21072.rar
Could you clarify or what you expect to be inside? Knowing if it is a game mod, a driver, or a work document would help me provide more specific instructions. Since Windows and macOS do not natively support extracting