A skeuomorph is a design feature that’s no longer needed but included because previous versions of the item (often made using different materials or in a different way) had whatever it is.

For example the decks of cruise ships are no longer made from planks of wood (as it’s a fire risk) but they’re likely to be finished in a brown material laid in strips to resemble planks. Modern compact cameras no longer have shutters, but they often make that distinctive cur-lick when a picture is taken, as they have a device added to reproduce it. Chocolates sometimes still come individually wrapped because back in the old days people didn’t always eat a whole tinful in one sitting …

Can you think of any more examples?