A layer that is not global, but it is taking it's content from a global layer, by having the same name, is marked as Overriden, because it's own content is being replaced by that of the global layer.
Before, this detail could only be seen in the Properties Bar next to the Global property of a layer.
Now the information is more visible, because it is also shown in the Layers Bar. It's only a cosmetic change, to make the information a little bit more clear.
Do mind that in the current beta there is bug where if you try to rename a layer which is global (or overriden), the part which is in parenthesis can become part of the real name of the layer. That has already been fixed.