The Free On-line Dictionary of Computing (30 December 2018):

gzip
gz

    GNU compression utility.  Gzip reduces
   the size of the named files using Lempel-Ziv LZ77
   compression.  Whenever possible, each file is replaced by one
   with the filename extension ".gz".  Compressed files can be
   restored to their original form using gzip -d or gunzip or
   zcat.

   The Unix "compress" utility is patented (by two separate
   patents, in fact) and is thus shunned by the GNU Project since
   it is not free software.  They have therefore chosen gzip,
   which is free of any known software patents and which tends
   to compress better anyway.  All compressed files in the GNU
   anonymous FTP area (gnu.org/pub/gnu) are in gzip
   format and their names end in ".gz" (as opposed to
   "compress"-compressed files, which end in ".Z").

   Gzip can uncompress "compress"-compressed files and "pack"
   files (which end in ".z").  The decompression algorithms are
   not patented, only compression is.

   The gzip program is available from any GNU archive site in
   shar, tar, or gzipped tar format (for those who already
   have a prior version of gzip and want faster data
   transmission).  It works on virtually every Unix system,
   MS-DOS, OS/2 and VMS.