Baking is a method of preparing food that uses dry heat, typically in an oven, but can also be done in hot ashes, or on hot stones. The most common baked item is bread, but many other types of foods can be baked. Heat is gradually transferred "from the surface of cakes, cookies, and pieces of bread to their center, typically conducted at elevated temperatures surpassing 150°C. Baking is a skill or way of cooking food in an oven. Sometimes, though, baking can also be done in hot ashes, or hot stones. It is used for making bread, cakes, pastries, pies, tarts, cookies, and much more. Such foods made by baking are called "baked goods". The ingredients used in baking include flour, water, leavening agents (baker's yeast, baking soda, baking powder), shortening (fats, oils), eggs, milk, and sugars. These are all mixed together to create dough or batter, which is then put into a pan or a sheet and heated. Leavening agents produce gas that becomes trapped in the dough. This makes it rise. Shortening makes doughs more easily workable and the bread that comes out in the end more soft and tender. Egg whites are used to help make a light, airy texture.
read more on wikipedia.