What does Judges 13:5 mean?

There was a certain man of Zorah, of the family of the Danites, whose name was Manoah; and his wife was barren, and childless.

Yahweh’s angel appeared to the woman, and said to her, “See now, you are barren and childless; but you shall conceive, and bear a son.

Now therefore please beware and drink no wine nor strong drink, and don’t eat any unclean thing:

Then the woman came and told her husband, saying, “A man of God came to me, and his face was like the face of the angel of God, very awesome. I didn’t ask him where he was from, neither did he tell me his name;

but he said to me, ‘Behold, you shall conceive, and bear a son; and now drink no wine nor strong drink. Don’t eat any unclean thing; for the child shall be a Nazirite to God from the womb to the day of his death.’”

Then Manoah entreated Yahweh, and said, “Oh, Lord, please let the man of God whom you sent come again to us, and teach us what we should do to the child who shall be born.”