Many of the indictors are self explanatory, but initially I dont understand the exact purpose of the following:
Raid Icon (Target) - I assume this is the raid icon of the target of the person who's frame you are looking at, but I have never seen this before so I am not sure
Aggro Blink/Bar: What is the difference between these (does the blink for a fixed amount of time after getting aggro)
Aoe Healing: I dont know what this does, I assume this is an indicator if some of your aoe healing spells are active on this player (for example wild growth active on that particular player)

It is also not clear to me what "NPC" or "Spotlight" means under the layout tab so having a tooltip of what these mean would also be nice.

will do something about "AoE Healing" indicator in the future.