Zest is the colored portion of the rind of the orange, lemon, or other citrus fruits. It is not the underlying white, pith portion of the peel.
Zest is a food ingredient that is prepared by scraping or cutting from the outer, colorful skin of unwaxed citrus fruits such as lemon, orange, citron, and lime. Zest is used to add flavor to foods.
You can buy special kitchen tools to zest citrus or you can use a small paring knife.