On a recent podcast episode a listener wanted to know if there is "junk" in .rar and .tar files. I don't deal with .rar files very often, and usually .tar files are the normal way to distribute programs in source format for compiling and installing.
What are .rar and .tar files? RAR [1] is a proprietary archive and compression format. I don't believe much software for Linux is distributed in RAR format. If RAR is used to distribute files, there probably are not many non-essential files. TAR [2] is a program that archives files and Linux software is often distributed in this format. TAR is also used for backing up systems and other backup programs often use tar [3]. One note, TAR does not compress archives by default, but can compress and uncompress archives with options to the TAR command.
