Depending on the hardness of the water where you live, small spots may appear on the heating element of your kettle when you use it. This is the result of scale build-up on the heating element and on the inside of the kettle over time.
The harder the water, the faster scale builds up. Scale can occur in different colours and although scale is harmless, too much scale can influence the performance of your kettle. Descale your kettle regularly to pro long the life of your kettle.