Let's begin with a Mea Culpa. A relative asked me what a 'microplane' zester is yesterday. Too often, I assume that 'everybody' just knows what stuff is, or how to use it. A quickly texted photo and a brief explanation saved the day.
I consider the Microplane zester a brilliant invention, and think it should be a part of every cooks' arsenal. It's my understand, based on an article I read years ago, that a woman invented it, after she (out of culinary desperation) used one of her husband's carpentry rasps to grate an orange. It's their story, and they're sticking to it.
This simple tool will find so many ways to be useful in your kitchen (grating chocolate bars over the top of a dessert?) - zesting citrus is the obvious place to begin. The Zest is that colorful part of the citrus skin. That's where the volatile oils are that deliver the amazing fragrance and flavor that we associate with citrus. To 'zest' (verb) is simply to remove that colored part from the underlying 'pith' - the white part.
Here's a link to a WikiHow video demonstrating how to 'zest' an orange. What I want you to note in the video, is how much harder it is to zest citrus on a regular hand grater with the larger holes. Scroll down to the section explaining the Microplane. See how effortlessly the orange glides down the microplaner? That's why you want one. It's not a bad idea to have both types, and perhaps a box grater in your arsenal.
Don't take it too far down into the white pith. That white part is bitter and not at all what you want.
The grated zest will accumulate in the underside of the Microplane zester, and you simply give it a couple taps on the cutting board, or over a container, to remove it. A large orange will deliver somewhere in the neighborhood of a couple of teaspoons or a tablespoon of zest. That's usually all you need for most recipes since the zest is pretty potent.
Here's another tip: If you're going to juice the orange, grate the zest first! I've made the mistake of juicing first and then trying to remove the zest from flaccid orange skins. If you're simply going to cut up the orange flesh, zest first, then with a sharp knife, cut around the orange to remove strips of the pith. Then segment the orange as you normally would.
Zesting an orange is necessary if you're going to make my cranberry sauce. See that small container of orange zest to the north of the pan? Yeah. That's what you're angling for.