What does Joshua 22:10 mean?

Now to the one half-tribe of Manasseh Moses had given inheritance in Bashan; but to the other half gave Joshua among their brothers beyond the Jordan westward. Moreover when Joshua sent them away to their tents, he blessed them,

and spoke to them, saying, “Return with much wealth to your tents, with very much livestock, with silver, with gold, with brass, with iron, and with very much clothing. Divide the plunder of your enemies with your brothers.”

The children of Reuben and the children of Gad and the half-tribe of Manasseh returned, and departed from the children of Israel out of Shiloh, which is in the land of Canaan, to go to the land of Gilead, to the land of their possession, which they owned, according to the commandment of Yahweh by Moses.

The children of Israel heard this, “Behold, the children of Reuben and the children of Gad and the half-tribe of Manasseh have built an altar in the border of the land of Canaan, in the region around the Jordan, on the side that belongs to the children of Israel.”

When the children of Israel heard of it, the whole congregation of the children of Israel gathered themselves together at Shiloh, to go up against them to war.

The children of Israel sent to the children of Reuben, and to the children of Gad, and to the half-tribe of Manasseh, into the land of Gilead, Phinehas the son of Eleazar the priest.