bzip2 is a compression program.

The bzip2 KIO worker is not directly usable, and is intended for use as a filter. For example, the tar KIO worker can filter a file through the bzip2 KIO worker, in order to display the contents of a tar.bz2 file directly in a Konqueror window.

If you click on a file compressed with a .bz2 in Konqueror, this KIO worker is used to uncompress it and display it as a normal (uncompressed) file.

If you are a developer, and would like to use the bzip2 filter, you can find documentation on using KIO workers at http://techbase.kde.org

See the manual: bzip2.

bzip is the ancestor of bzip2. It is rarely used today, having been replaced with bzip2, which offers much better compression.