Coming from the Windows world most of us people know the .rar archive format very well. Besides the newer 7zip format, Rar allows a good compression and is widely used on internet distribution.
II. What do we need?
People who only need to have a decompressor for compatibility reasons can use MacPar Deluxe. Users who also want to be able to compress files aswell need to get SimplyRar:
III. How do these tools work?
MacPar Deluxe is intended for unpacking only. The part of the name Par indicates its main use, as it is a tool for people downloading things from the usenet. Par files are files that contain repair information for damaged main files. Anyway: MacPar Deluxe also contains a very simply unrar engine.
SimplyRar is a graphical user interface for the free command line version of rar for Mac OS. It contains (almost) all features of the command line. As a switcher I currently cannot tell what features are missing in comparison to WinRar for Windows.