What does Numbers 35:9-34 mean?

And the LORD spoke to Moses, saying, “Speak to the people of Israel and say to them, When you cross the Jordan into the land of Canaan, then you shall select cities to be cities of refuge for you, that the manslayer who kills any person without intent may flee there. The cities shall be for you a refuge from the avenger, that the manslayer may not die until he stands before the congregation for judgment. And the cities that you give shall be your six cities of refuge. You shall give three cities beyond the Jordan, and three cities in the land of Canaan, to be cities of refuge. These six cities shall be for refuge for the people of Israel, and for the stranger and for the sojourner among them, that anyone who kills any person without intent may flee there. “But if he struck him down with an iron object, so that he died, he is a murderer. The murderer shall be put to death. And if he struck him down with a stone tool that could cause death, and he died, he is a murderer. The murderer shall be put to death. Or if he struck him down with a wooden tool that could cause death, and he died, he is a murderer. The murderer shall be put to death. The avenger of blood shall himself put the murderer to death; when he meets him, he shall put him to death. And if he pushed him out of hatred or hurled something at him, lying in wait, so that he died, or in enmity struck him down with his hand, so that he died, then he who struck the blow shall be put to death. He is a murderer. The avenger of blood shall put the murderer to death when he meets him. “But if he pushed him suddenly without enmity, or hurled anything on him without lying in wait or used a stone that could cause death, and without seeing him dropped it on him, so that he died, though he was not his enemy and did not seek his harm, then the congregation shall judge between the manslayer and the avenger of blood, in accordance with these rules. And the congregation shall rescue the manslayer from the hand of the avenger of blood, and the congregation shall restore him to his city of refuge to which he had fled, and he shall live in it until the death of the high priest who was anointed with the holy oil. But if the manslayer shall at any time go beyond the boundaries of his city of refuge to which he fled, and the avenger of blood finds him outside the boundaries of his city of refuge, and the avenger of blood kills the manslayer, he shall not be guilty of blood. For he must remain in his city of refuge until the death of the high priest, but after the death of the high priest the manslayer may return to the land of his possession. And these things shall be for a statute and rule for you throughout your generations in all your dwelling places. “If anyone kills a person, the murderer shall be put to death on the evidence of witnesses. But no person shall be put to death on the testimony of one witness. Moreover, you shall accept no ransom for the life of a murderer, who is guilty of death, but he shall be put to death. And you shall accept no ransom for him who has fled to his city of refuge, that he may return to dwell in the land before the death of the high priest. You shall not pollute the land in which you live, for blood pollutes the land, and no atonement can be made for the land for the blood that is shed in it, except by the blood of the one who shed it. You shall not defile the land in which you live, in the midst of which I dwell, for I the LORD dwell in the midst of the people of Israel.”