Broth is a flavorful liquid made by simmering bones, meat, or vegetables, while soup is a dish that incorporates broth along with solid ingredients like vegetables, meat, or noodles. A broth becomes a soup when additional ingredients are added to it.
The key difference lies in the ingredients and the intended use. Broth is primarily a liquid, created by simmering animal bones (chicken, beef, fish), meat, or vegetables in water. The purpose of simmering is to extract flavor and nutrients from these ingredients into the liquid. Broth can be seasoned with herbs and spices, but it generally remains a clear liquid. It's often used as a base for other dishes.
Soup, on the other hand, is a more complex dish. It always contains a liquid base, which can be broth, stock, or even water. However, soup also includes solid ingredients such as vegetables, meat, poultry, fish, pasta, rice, or beans. These ingredients are cooked within the liquid, adding texture and substance to the dish. The addition of these solid components transforms a simple broth into a complete and satisfying soup. Think of it this way: broth is an ingredient, while soup is a finished dish.
Don't over-salt your broth! Remember that the flavor will concentrate as it simmers, and you can always add more salt later when you're making the soup. It's much harder to remove salt if you add too much early on.