The Tape ARchive format. (MIME-type: application/x-tar) An archive file format used mostly in the Unix world. tar is capable of storing the file system structure including file permissions and dates. It was originally used for performing sequential writes to tape devices -- mostly for backup purposes. After the "-f" command switch was introduced tar could also be written to files.
tar does not do any compression by itself, so it's not a compression format like, for instance, zip. One can compress tar archives using either a separate tool or commandline switches -j (bzip2), -z (gzip) or -Z (compress). The commandline switches are available in the GNU version of tar.
The common extensions for tar files are:
Related software tools
7-Zip (Open source)
7-Zip is a free compression software that can create and open .zip, .rar and .7z file formats, among others.