Weathering nodes take Mask Generators ones step further: they do a full-material weathering effect based on parameters and baked maps. The concept is very similar to Smart Materials in Substance Painter.
You need to have one or more baked maps to get a full result out of these nodes.
Keep in mind that because these nodes offer such all-encompassing, complete effects, their usage is limited to only some cases. However, they can also be a good base for learning how such complex effects are built. Drag the nodes from the library into the Explorer, or right-click and choose "Open Reference" on a node placed in the graph.