Bread crumbs are made by grinding stale bread, and they have all sorts of uses around the kitchen. Many companies sell them already made, usually in airtight containers so that they do not get soggy. It is also possible to make bread crumbs at home from unused bread which has gone stale. These can be stored in the freezer until they are needed. Many are also seasoned, in which case they can be used for specific things. Keeping them unseasoned allows a cook to use them in a wide variety of situations, so many cooks keep plain crumbs around instead.
One of the classic uses for bread crumbs is as a breading. Breading is a layer on the outside of food that is fried or sauteed. Typically, the food is dredged in a milk and egg mixture before being lightly brushed with flour and then rolled in bread crumbs. The crumbs make a crispy, flavorful outer coating that also helps to prevent the inside of the food from getting greasy.
Like bread, bread crumbs also make excellent filler in things like quiches, frittatas, and puddings. One variety of bread pudding is made with crumbs, rather than chunks of bread, for example. They will also give a quiche more body and help to make foods seem less heavy. In addition, they will reduce the overall cost of a dish such as a frittata by decreasing the amount of eggs and other expensive ingredients needed.
Many casseroles also call for a topping of bread crumbs, which form a browned, crispy crust on the surface of the cooked dish. In this case, lightly seasoned crumbs are usually dressed with butter or oil before baking, so that they will brown in the oven. A baked dish topped this way will have more texture, and the inside will be more moist and flavorful, since the top layer keeps the innards from drying out.
Ingredients like celery, carrots, and water chestnuts can be mixed with bread crumbs and other seasonings for a savory stuffing. Seasoned vegetables such as artichokes, zucchini, and bell peppers can be stuffed thusly, and crumbs can also be used for more ambitious stuffing projects, like turkey. For larger stuffings, they usually form a smaller proportion of the total ingredients, so that they do not wind up in a solid mass.
As many readers of fairy tales know, bread crumbs can potentially be used to lay a trail. However, in regions with large animal populations, such a trail tends to be eaten, so woodland adventurers may want to consider carrying more long lasting trail markers such as small stones or surveyors tape.