bzip2(1) is an alternative compression program installed on Slackware Linux. It uses a different compression algorithm from gzip, which results in some advantages and some disadvantages. The main advantage for bzip2 is the compressed file size. bzip2 will almost always compress better than gzip. In some instances, this can result in dramatically smaller files. This can be a great advantage for people on slower modem connections. Also remember, when downloading software from a public ftp server, it's generally good netiquette to download the .bz2 files instead of the .gz files, as this results in less overhead for the generous people hosting the server.
The disadvantage to bzip2 is that it is more CPU intensive than gzip. This means that bzipping a file will generally take longer and will use more of the CPU than gzipping the file would. When considering which compression program to use, you must weigh this speed vs. compressed size and determine which is more important.
The usage of bzip2 is nearly identical to gzip, so not much time will be spent discussing it. Like gunzip, bunzip2 is identical to bzip2 -d. The primary difference in practical usage is that bzip2 uses the .bz2 extension.
% bzip2 filename % bunzip2 filename.bz2 % bzip2 -9 filename