kill by itself will cause a process to try to finish what it's doing and save it's state before actually stopping the process, if you pass it the -9 option it will instead kill a process immediately and without waiting or saving any state/information. The HUP flag will cause the process to re-read it's configuration file (basically a restarting of the process).
-1 HUP; be careful with this, if used as root, this goes to ALL processes. -HUP the same as -1 -6 abort, like doing a control-C -9 uninterruptible kill -- stop the process NOW -15 kill politely (save changes, stop when done)
See also skill