What does Joshua 4:10 mean?

then you shall tell them, ‘Because the waters of the Jordan were cut off before the ark of Yahweh’s covenant. When it crossed over the Jordan, the waters of the Jordan were cut off. These stones shall be for a memorial to the children of Israel forever.’”

The children of Israel did as Joshua commanded, and took up twelve stones out of the middle of the Jordan, as Yahweh spoke to Joshua, according to the number of the tribes of the children of Israel. They carried them over with them to the place where they camped, and laid them down there.

Joshua set up twelve stones in the middle of the Jordan, in the place where the feet of the priests who bore the ark of the covenant stood; and they are there to this day.

When all the people had completely crossed over, Yahweh’s ark crossed over, with the priests, in the presence of the people.

The children of Reuben, and the children of Gad, and the half-tribe of Manasseh, crossed over armed before the children of Israel, as Moses spoke to them.

About forty thousand men, ready and armed for war passed over before Yahweh to battle, to the plains of Jericho.