Well the daylight and actinic bulbs provide your daytime lights. Some people like to run actinic bulbs for an hour before and after the daylight bulbs so as not to "shock" fish and corals by suddenly going from dark to light. The actinics also make some corals fluoresce under them and its pretty neat to see. The moonlight is used for night viewing or moonlight simulation.
Most people set their daylight bulbs for about 10-12 hours. The actinics for either 10-12 or an hour extra on either side of the daylight. And the moonlight bulbs are on while the others are off or for a few hours at night.
