When kidneys fail. End stage renal disease is stage five CKD or GFR 15 or less. Dialysis is started when the function of the kidneys is inadequate to remove the metabolic byproducts of metabolism. In practice this is usually determined by measuring gfr. Most people have to start dialysis when GFR drops to 10-15 though it may have to be started higher or lower than that.
Yes, or transplant. Speak with a nephrologist (kidney specialist) different types of dialysis : hemodialysis, peritoneal, or transplant. Need will depend on whatever stage kidney disease and blood tests.