1. is a relatively new algorithm for compressing data. It generally achieves files that are 60-70% of the size of their gzipped counterparts. From Bzip2 mini-HOWTO

2. A high-quality block-sorting file compressor - utilities bzip2 is a freely available, patent free, high-quality data compressor. It typically compresses files to within 10% to 15% of the best available techniques, whilst being around twice as fast at compression and six times faster at decompression. bzip2 compresses files using the Burrows-Wheeler block-sorting text compression algorithm, and Huffman coding. Compression is generally considerably better than that achieved by more conventional LZ77/LZ78-based compressors, and approaches the performance of the PPM family of statistical compressors. The archive file format of bzip2 (.bz2) is incompatible with that of its predecessor, bzip (.bz). From Debian 3.0r0 APT

3. Bzip2 compresses files using the Burrows-Wheeler block-sorting text compression algorithm, and Huffman coding. Compression is generally considerably better than that achieved by more conventional LZ77/LZ78-based compressors, and approaches the performance of the PPM family of statistical compressors.The command-line options are deliberately very similar to those of GNU Gzip, but they are not identical. From Mandrake 9.0 RPM

4. Bzip2 is a freely available, patent-free, high-quality data compressor that uses the same command line flags as gzip. From Redhat 8.0 RPM