When you view a measure in the Model tab, it's easy to see where in the model hierarchy the measure belongs. In the example below, we can visually relate the measure named "DTD" to it's parent metric and parent measure.
A possible problem arises though, if you have more than one measure named DTD (e.g. Filler 2 also has a Total Production measure with a Day-To-Date (DTD) aggregation. Now, if you put both these measures named "DTD" in a report, you cannot easily tell them apart.
This is why Measures are identified by their Hierarchical Name. The Hierarchical Name is made up of the entities in a measure’s containment structure.
A measure’s hierarchical name is displayed in the top left of the measure’s configuration editor (e.g. in the image below, the measure's hierarchical name is Filler 1.Total Production.DTD)