No sweat. I didn't know what a refugium was at one point either. IMO
there are no drawbacks to having a refugium only benefits. The need for one is debatable, but a great addition at any rate. In short: a refugium is a sump like container that holds additional substrate (mud, sand, LR
rubble, anything else) that adds additional filtration and usually macro algeas (saltwater plants). The macros remove exessive nutrients from the water column (like a natural skimmer kinda) and they also provide a safe haven for pods
to grow without predation. They can serve as a small hospital for corals or segragation units for fish.
Refugiums come in different styles. There are small Hang-On-Back refugiums that water is pumped into with a PH
and gravity flow back into the display. (basically small acrylic boxes that sit just above the waterline on the back of hte tank. There are sump/refugiums that sit under that tank and is fed just like a sump and pumped back up into the display. There are even IN-tank refugiums. They are small boxes that sit inside your tank, but IMO
are not large anough to provide the real benefit of a refugium and cram up the tank.
So, no you don't NEED one, but they are nice to have and add not only filtration, but nutrient export, more water volume for stability, and other benefits.