BZ2 are compressed files generated using the BZIP2 open source compression method, mostly on UNIX or Linux system. It is used for compression of a single file and is not meant for archiving of multiple files. This is in contrast to the TAR file format on the same platforms that archives multiple files into a single file but without compression. Files compressed as BZ2 can be decompressed with applications like WinZip. BZIP2 uses Run-Length Encoding (RLE) or Burrows-Wheeler compression algorithm to achieve high levels of compression. Learn more about this file format here.