The role of vanilla in sweet baked goods is like the role of salt on the savory side: it enhances all the other flavors in the recipe. Without it, cookies and cakes tend to taste flat and bland. Forget to add the vanilla once, and you'll probably never do it again!
Vanilla extract is made by steeping whole vanilla beans in a mixture of alcohol and water. Both the seeds inside the pod and the pod itself give flavor to the extract, and letting them age together for a while makes the flavor deeper and more complex. If you have vanilla beans (or even just their pods) to use up, try your hand at making your own extract.
Cakes to cookies, marshmallows to buttercream frosting: none of these recipes is complete without a drop of vanilla extract. It seems like such a small, almost trivial ingredient in comparison to the rest of the recipe, but we are mighty glad it's there!
What's your favorite brand of vanilla extract?