What does Exodus 12:28 mean?

It shall happen when you have come to the land which Yahweh will give you, according as he has promised, that you shall keep this service.

It will happen, when your children ask you, ‘What do you mean by this service?’

that you shall say, ‘It is the sacrifice of Yahweh’s Passover, who passed over the houses of the children of Israel in Egypt, when he struck the Egyptians, and spared our houses.’” The people bowed their heads and worshiped.

At midnight, Yahweh struck all the firstborn in the land of Egypt, from the firstborn of Pharaoh who sat on his throne to the firstborn of the captive who was in the dungeon; and all the firstborn of livestock.

Pharaoh rose up in the night, he, and all his servants, and all the Egyptians; and there was a great cry in Egypt, for there was not a house where there was not one dead.

He called for Moses and Aaron by night, and said, “Rise up, get out from among my people, both you and the children of Israel; and go, serve Yahweh, as you have said!