What does vanilla extract add to a recipe? I have been cooking for a while and have noticed small amount of Vanilla extract needed in cakes, cookies, muffins, even a smoothie recipe.  Often times I forget the Vanilla or don't have any.  What am I losing in general in a recipe without any Vanilla Extract?

Then in this recipe 1 cup yogurt, 1 banana, 4-6 cups milk, 1 peach, 1 teaspoon vanilla extract what does the Vanilla add or subtract?
Vanilla extract adds the flavour of vanilla! Not as nice as using a real vanilla bean, but significantly cheaper and much easier to get hold of.