This is the technical gold. RAR refers to the compressed archive format ( .rar ) used to package files. Hot is a descriptor used in file-sharing communities (torrents, forums, blogs) to indicate a recently uploaded, high-demand, or high-bitrate (often 320kbps MP3 or FLAC) file. When combined, "the cardigans the best of rar hot" points directly to a user-assembled, premium, lossless or near-lossless digital compilation.
The Cardigans were prolific. Their B-sides weren't throwaway tracks; they were often experimental detours that showed off the band's incredible musicianship. If you are compiling your own "Best of Rar" playlist, here are a few tracks that are absolutely essential to understanding the band’s scope: