Difference between two tar commands -cf and -Jchf

I have a python script that is running in two places, two different, but similar commands: os.system("tar cf - -C %s . 2>/dev/null 3>/dev/null | 7za a -p%s -si %s 1>/dev/null 2>/dev/null 3>/dev/null" % (cf, self.config.get(jn, "archpass"), filename)) os.system("tar -Jchf - -C %s . 2>/dev/null 3>/dev/null | 7za a -p%s -si %s 1>/dev/null 2>/dev/null 3>/dev/null" % (cf, self.config.get(jn, "archpass"), filename)) This script is used to backup websited on a Ubuntu server. So most of files are html/php/js/jpg. I need to understand this command more in order to have an idea if there is place for improvement. **Question 1)** What's the difference between: tar cf and tar -Jchf. Unfortunately tar --help didn't help me understand the additional -Jf parameters. **Question 2)** Is tar also archiving? What could be the purpose of sending everything to 7za? Is it doing a double archivisation?