There are several potential causes of white gums. One simple cause is the collection of food and other debris along the edge of the gums where they contact they teeth. If the white discoloration is limited to this part of the gums in your case, this may be what is going on, and the condition should respond to improved brushing, although you probably also would need to see your dentist
for a formal teeth cleaning.
If the white areas of the gums are not limited to the edges of the teeth but are rather flat areas that cover the roof of your mouth, cheeks, or other similar areas then there are at least two possibilities. The first is that you have thrush, which is a fungal infection of the mouth; in this condition, you can usually scrape of the white areas, although the tissue underneath may bleed. The second condition is leukoplakia, which is a precancerous condition that tends to occur mostly in those who use tobacco or alcohol; these spots cannot be scratched off.
You should go see either your dentist or your primary care doctor
; both of them will be able to diagnose what is going on and help you figure out what to do next.