Balance scales are tools used to measure weight by comparing two objects. They consist of a beam that is supported at its center, with two pans hanging from either end. When an object is placed in one pan, the scale will tip until the weights in both pans are equal, indicating the weight of the object. These scales operate on the principle of equilibrium, where the forces on both sides are balanced. They are commonly used in laboratories, kitchens, and educational settings to teach concepts of weight and measurement. Balance scales can also be found in various forms, such as digital scales and spring scales.