In computing, tar (derived from tape archive) is both a file format (in the form of a type of archive bitstream) and the name of a program used to handle such files. The format was created in the early days of Unix and standardized by POSIX.1-1988 and later POSIX.1-2001. Initially developed to write data to sequential I/O devices for tape backup purposes, tar is now commonly used to collect many files into one larger file for distribution or archiving, while preserving file system information such as user and group permissions, dates, and directory structures.
Bzip2 is a free program developed under BSD license that compresses and decompresses files using compression algorithms Burrows-Wheeler and Huffman coding. The compression ratio achieved depends on the contents of the file to be compressed, but usually is far better to compressor based on the algorithm LZ77 / LZ78 (gzip, compress, WinZip, PKZip, ...). In return, bzip2 uses more memory and execution time.