When the kidneys are not functioning properly and the GFR (Glomerular filtration rate, an index of kidney function) is less than 100ml /min, it is called Renal Failure. It has different varieties.

ACUTE RENAL FAILURE (ARF) 

When the kidneys suddenly stop working and the waste products accumulate in the body, it is called Acute Renal Failure.

CHRONIC RENAL FAILURE 

When the kidney functions are deranged for more than three months it is called Chronic Renal Failure. Chronic renal failure may be due to Isolated kidney disease such as chronic Glomerulonephritis, Renal Stone diseases, Reflux nephropathy, and longstanding infection of the kidneys called Chronic Pyelonephritis.

Systemic illnesses in which kidneys may be affected along with other organs, such as longstanding diabetes and hypertension.

END STAGE RENAL DISEASE (ESRD)

End Stage Kidney disease is called when 

1. GFR is reduced to less then 15% in diabetic nephropathy, and less then 10% in non diabetic renal failure.
2. Patients cannot survive without renal replacement therapy (RRT)
3. There is no reversible factor in renal disease.