Could someone explain the Avenger of Blood in the bible?

The one authorized under the law of Israel to avenge the blood of one who had been killed was called the “avenger of blood” or go‧ʼel′ and was the nearest male relative of the one slain. (Num. 35:19) Since the nearest of kin would be personally involved with the one slain, it is understandable that he would have a keen interest in fulfilling this responsibility, even rising up in the heat of anger to avenge the life of his kinsman. If the murderer was known, then atonement for the blood of the slain man must be swift and certain. “In case there should happen to be a man hating his fellowman, and he has lain in wait for him and has risen up against him and struck his soul fatally and he has died, and the man has fled to one of [the cities of refuge], the older men of his city must then send and take him from there, and they must deliver him into the hand of the avenger of blood, and he must die. Your eye should not feel sorry for him, and you must clear away the guilt of innocent blood out of Israel, that you may have good