tar xfz and friends

Extract a gzipped tar archive ( *.tar.gz ):

tar xfz archive_name.tar.gz

Extract a tar archive (*.tar):

tar xf archive_name.tar.gz

Create an uncompressed tar archive:

tar cf archive_name.tar dirname/

Create a gzipped tar archive:

tar czf archive_name.tar.gz dirname/

More examples: https://www.thegeekstuff.com/2010/04/unix-tar-command-examples/