Chronic kidney disease (CKD), chronic renal disease, chronic renal failure (CRF) are all describing the same medical condition in your cat. Most professionals have settled on using the term chronic kidney disease (CKD). The other terms were often coined by various researchers who wanted their published paper to stand out among all the other papers being published over the years. The definition of each term is the same and you will be able to use the information provided by each term above, to help you understand your cats condition.
Acute renal failure is different and is usually used to describe kidney damage due to a physical injury or poisoning. It is sudden and progression is quick, usually within a few days to weeks.