In eagle there are two kinds of labels. "Plain" ones and ones with arrows. In the toolbar these are labeled as "Xref on" ("Plain") and "Xref off" ("Arrow"). Is there a functional difference between the two (I cannot find anything) and what exactly does "Xref" do?
XREF labels connect nets between pages and are called out because they represent inputs and outputs to the page you're currently viewing. Non-XREF labels are internal and are connected to other nets with the same name on the page you're currently viewing.