Depending on the pH of your tap water, you may get limescale stains on your washbasin and around the shower and tap nozzles. These are hard and therefore often difficult to remove if you don't know how. When you do, it's really easy. :-)
Soak a cloth or paper in vinegar essence and rub the stains. If the stains are very hard you can let the soaked cloth lay on the stain for a while. Then it will easily be removed.