The help command displays on-line help. To specify information on a particular topic use the syntax:
help {<topic>}
If <topic> is not specified, a short message is printed about
GNUPLOT. After help for the requested topic is given, help for a
subtopic may be requested by typing its name, extending the help
request. After that subtopic has been printed, the request may be
extended again, or simply pressing return goes back one level to the
previous topic. Eventually, the GNUPLOT command line will return.