Not supposed to "whiten" the skin, as in make it white, but helps with pigmentation. An increase in melanin in skin can cause dark spots such as freckles, or scars from acne can cause skin discolouration. So when they say "whiten" it just is helping lighten the discolouration of your skin to give it an even skin tone, and overall will help you have a more revitalized look to your skin.
It does take a few months for skin tone and dark spots to improve. Skin regenerates itself over a process of 28 days, so after many layers it will improve.
The Essence is a liquid lotion, rather than a thick cream. Toner helps to remove any last impurities and reset the balance of skin after using a face wash or soap. You could probably use it as a toner.