In general, kidney failure means that your kidney function is really bad. In general, the definition for kidney failure is eGFR less than 15ml/min/1.73m^2. Kidney failure often refers to "chronic kidney failure". However, in medicine, there is also a common condition called "acute kidney failure (more precisely known as acute kidney injury). Both conditions could cause your kidneys to shut down. The difference is that the kidney shutdown in chronic kidney failure is generally irreversible, while in the acute kidney failure it is reversible. To put it in another way, with chronic kidney failure, you practically could do nothing to get your kidney healed. You have to rely on dialysis or kidney transplants to be alive for the rest of your life. However, with acute kidney failure, most patients would recover and do not need dialysis/transplant.