What does Leviticus 20:22 mean?

“‘You shall not uncover the nakedness of your mother’s sister, nor of your father’s sister; for he has made his close relative naked. They shall bear their iniquity.

If a man lies with his uncle’s wife, he has uncovered his uncle’s nakedness. They shall bear their sin. They shall die childless.

“‘If a man takes his brother’s wife, it is an impurity. He has uncovered his brother’s nakedness. They shall be childless.

You shall not walk in the customs of the nation, which I am casting out before you: for they did all these things, and therefore I abhorred them.

But I have said to you, “You shall inherit their land, and I will give it to you to possess it, a land flowing with milk and honey.” I am Yahweh your God, who has separated you from the peoples.

“‘You shall therefore make a distinction between the clean animal and the unclean, and between the unclean fowl and the clean: and you shall not make yourselves abominable by animal, or by bird, or by anything with which the ground teems, which I have separated from you as unclean for you.