Learn more about a command

	$ whereis [command]		# locate the binary, source, and manual page files for a [command]
	$ whatis [command]		# display one-line manual page descriptions
	$ which [command]		# shows the full path of (shell) commands.
	$ apropos [command]		# search the manual page names and descriptions	
	$ man [command]			# an interface to the on-line reference manuals
	$ info [command]		# read Info documents