Train categories in Europe
In Europe, railway companies assign trains to different categories or train types depending on their role, i.e. based on the used rolling stock, their speed (high-speed, higher-speed, conventional), distance of travel (long, medium, short), stopping frequency (Inter-city, limited express, express, limited-stop, regional, commuter) and other criteria.
Source: Wikipedia — Train categories in Europe (CC BY-SA 4.0)