United States cooking schools often differentiate between "broth", usually made from portions of animal meat, and "stock" often made from vegetable scraps and bones.
In the most basic terms, stock is the strained liquid that is the result of cooking vegetables, meat or fish and other seasoning ingredients in water. Most soups begin with a stock of some kind, and many sauces are based on reduced stocks. It is also known as broth, is a liquid derived from slowly simmering poultry, meat, fish, or vegetables in water, along with herbs. It is used as a primary cooking liquid or to moisten or flavor foods as they cook. Stock may be made from beef bones, chicken bones and parts, fish skeletons, lamb bones, or a variety of vegetables. Stocks can be made by the home cook and stored in the refrigerator or freezer for future use. Some, such as beef, chicken, and fish, are available canned, frozen, or in concentrated form.
Broth is a liquid in which meat, fish, cereal grains, or vegetables have been simmered and strained out. Broth is used as a basis for other edible liquids such as soup, gravy, or sauce. It is very flavourful and can be eaten alone or with garnish. Many consider it "common knowledge" that broth differs from soup stock, in that stock requires only water and bones; or that broth is not cooked as long as soup stock and does not have as full a flavour; or that stock is used as an ingredient and broth refers to a final product. While each of these definitions are popular and see general usage, they are not universally accepted, and often the terms are used interchangeably (as in "vegetable stock," or a liquid that's been bade with both meat and bones served as soup).
In East Asia (particularly Japan), a form of kelp called kombu is often used as the basis for broths (called dashi in Japanese).