A. Zest is the outermost rind of citrus fruits (usually lemons and oranges). It is valued for the strong citrus flavor it imparts to food, thanks to an abundance of perfumy, aromatic oils in the rind.
To remove the zest from the fruit, use a utensil called a zester or a sharp paring knife or vegetable peeler. Peel off only the colored portion of the rind; the white pith can be bitter rather than flavorful. Then mince or leave it in strips as the recipe dictates.
Some recipes call for grated zest. You can simply grate the lemon or orange as you would any vegetable, using a hand-held grater. Again, be careful that you are grating only the colored part of the rind.
Alternatively, you can purchase dried zest in the spice section of the supermarket, but it doesn't hold a candle to the real thing.