Vanilla beans are actually the long, thin pod of an orchid plant. The pod is dried and cured but should not be eaten. Instead, the tiny seeds inside the pod are what you actually use. They have the intense vanilla flavor . When a recipe calls for vanilla beans, follow the recipe's directions for extracting the seeds from the pod. Some will call for the pod to be heated in a liquid mixture to make it easier to split open, but even a dry vanilla bean can be cut lengthwise and a with a paring knife allowing you to open and scrape out the tiny seeds. After the seeds have been removed you can use the pod to make vanilla sugar.
If the recipe calls for vanilla beans and you don't happen to have one on hand, you can usually substitute 2 teaspoons of vanilla for 1 vanilla bean.