What does stage 3 kidney disease mean?

Loss of function: Kidneys of human body has millions of microscopic filters to eliminate waste , called glomurali , due to diabetes , blood pressure , and age etc we lose them , non reversible filtration rate will decrease , as more of them are gone, ultimately leads to end stage renal failure dialysis is required , , stage iii a rate will be 45-59 ml/mint in stage iii b will be 30 - 44 ml/ mnt.