Scaling sounds worse than it is.  It is just a method of cleaning teeth  and removing plaque and tartar (hardened plaque) used by dentists. It cleans above and below the gumline.  It is not possible to remove tartar by brushing and flossing alone, so it has to be removed regularly.

If tartar builds up under the gums it can lead to gum disease and a range of other problems including losing your teeth.