Low light corals are deep water corals that do not require bright light to live. Many corals fit into this catagory. On many web sites and on other marine sites look for corals stating that flourescent lights are OK.
All polyps, many leather corals, mushrooms, some Brain corals just to name a few, do not require much light. A few anenome's are low light deep water as well, but most require medium to high light so make sure it states low light.
How much light do you have? When people say low, medium, high = each grade is in the eye of the beholder, means different things to different people.
Hope that helped
Thomas