What does Joshua 22:3 mean?

The people of Israel heard about it and said, 'Look, the tribes of Reuben, Gad, and the half-tribe of Manasseh have built an altar right on the border of Canaan, by the Jordan, on Israel’s side.' Joshua 22:3 - Modern Text Bible

(Word spreads quickly about the new altar, and it’s seen as a big deal because of its location and size.)