Zest is the colourful part; peel and rind are the same thing. Peel/rind is both the colour and the white pith.
Zest appears as an ingredient in recipes for adding the flavour of the fruit. When eating citrus, don’t let things go to waste – use a grater and do the whole thing. You can store the zest in airtight bags in the freezer. Being so small, thawing takes no time if you want to use zest in dressing, soup, sauce, sorbet, etc.
However there is a caveat for those of us on medications. Citrus zest has been found to have furanocoumarins, the class of chemical compound that can play havoc with your medication (known as The Grapefruit Effect).