bzip2 .bz2 is the filename extension associated with the bzip2 data compression format. It is an open source data compression and decompression tool developed by Julian Seward in 1996. The compression and decompression format is cross platform compatible and comes bundled with versions of Linux and UNIX. The latest of Bzip2 exists as an open source library for download and customization. Earlier versions have executables that can be run directly on Microsoft Windows.
tar The .tar filename was originally designed to be used as a TApe ARchiver to store entire file systems and files as single files on tape storage medium. It was designed by AT&T in 1979. Today, the format more commonly refers to an archive or collation of multiple files into a single file with the .tar filename extension. The format is an open source file archive format commonly associated with the UNIX tar command however other data compression tools are capable of effectively compressing and/or decompressing files saved with the .tar file format. Doing so typically adds the compression filename extension to the archive file for example .tar.bz2.