Fluid. It means that you have a fluid build up in your sinuses, usually mucous. The ethmoid sinuses are directly behind your nose, and the sphenoid sinuses behind that. The fluid was only seen on the right side.
Inflammation. It may refelct some inflammation of the lining of your sinuses or some mucus build up. Could be chronic or acute but if you are not symptomatic there's no treatment needed for it. Follow up with your ent.