Broth is a liquid in which meat, seafood, cereal grains, or vegetables have been simmered and strained out. Broth is similar to stock; however, stock typically includes bones and/or other off-cuts, and it is typically simmered longer than broth for a more intense flavor. Broth also contains less gelatin than stock since it does not use bones and cartilage. Despite these differences, the terms 'stock' and 'broth' are sometimes used interchangeably.
Broths can be concentrated into pastes or powders and sold commercially—these are often referred to as 'bouillon'. Their shelf life without preservatives is limited. Commercial preparations also often have large amounts of salt and/or MSG added. Bouillon cubes in particular have more salt than flavor and will alter the final recipe in many cases if substituted for fresh broth.
Broth can be slowly simmered until it is clarified and substantially reduced (by at least 50%) to make consommé, which has a substantially more intense flavor. When it is necessary to clarify a broth for a cleaner presentation, egg whites may be added during simmering—the egg whites will coagulate, trapping sediment and turbidity into a readily strainable mass.