A GZIP file is a compressed archive that is created with the standard gzip (GNU zip) compression algorithm. The compressed archive may contain multiple files including compressed files, directories and file stubs. Most of the Unix systems include the open source gzip (GNU Zip) compressor utility for compression/decompression of files. GZIP files can be opened with applications such as WinZip.
GZIP File Format - More Information
GZIP uses the DEFLATE algorithm to compress files to archives. Two RFCs, RFC1952 and RFC 1951, define the specifications of the gzip wrapper format and deflate compressed data format, respectively.