There are two categories for teeth whitening. First is extrinsic the removal of surface discoloration. Brushing your teeth is extrinsic whitening by physically removing colored biofilm adhering to teeth and uncovering the natural enamel underneath.

There there is intrinsic, changing the color of the tooth. Chemical bleaching is  intrinsic whitening it penetrates the surface and actually whitens the enamel. The bleaching procedure can be done professionally at a dental office or be a prepared product either in a dental office or at home under dentist supervision. It also can be done at home using over-the-counter products you can buy in most food stores.  You may want to talk over your whitening options with your dentist to find out what is the best choice for you.