Hi E
A sump is simply a tank below your dispaly tank that is plumb in and used for the following

Increasing Overall Water Qty
Gets the Skimmer, External, Internal Filter, heater etc.out of the main tank
(I will put a link that shows a list of sumps styles when I get home tonight)
Powerheads are Small Submersible Pumps that create flow in a tank, IMO you need around a Flow of 20x total volume of the tank
Pump for operating sump

is a pump that pumps water from the sump up to the main tank.
Lighting IMO doesnt have to be Metal Halides if you only plan on a Fish Only or Fish Only with Soft Corals, you will get away with either T5 Bulbs or a T5 Lumanaire
That list given IMO is a must if you want to be sucessful.
Live rock is very important as is the powerheads that creat a flow over the Live rock thuis feeding it (Well the bacteria on it)
Del
