The principle of buoyancy that explains why objects float is known as Archimedes’ principle. This principle states that any object submerged in a fluid experiences an upward buoyant force equal to the weight of the displaced fluid. If an object's weight is less than the weight of the fluid it displaces, it will float; if it is more, it will sink. This principle is fundamental in understanding how objects interact with fluids, shaping applications such as ship design and swimming, and is crucial in various fields of physics and engineering.