pkill is related to the pgrep utility. If, for example, you typed pkill -HUP inetd, it would search for a running process with that name and sent it a SIGHUP signal (in this example inetd would then re-read its configuration file).
It replaces having to type ps -ef | grep inetd to find the process ID, and then type kill -HUP 123.
So the answer to your second question is probably yes, depending on what processes the SIGHUP was sent to.
Annihilannic.