Please Explain To Me What Stage 3A Chronic Renal Insufficiency

Please explain to me what stage 3A chronic renal insufficiency is? The only diagnosis ever received from my primary care dr. is a lab result showing my filtration rate not in a normal range. The only recommendation to me from ny dr. has been to stay hydrated. The reason I am asking this question is I had recently applied for long term health care insurance, but have been turned down because of this showing up in my medical records. I have not been concerned until now as my dr. has never recommended any sort of treatment, and I seem to be healthy otherwise. If possible, please advise me. Thank you