Buoyancy is a force that acts on objects submerged in a fluid, allowing them to float or rise. It is the result of a pressure difference between the top and bottom of the submerged object. The principle of buoyancy is described by Archimedes' principle, which states that an object will float if the weight of the fluid it displaces is greater than or equal to its own weight. This concept is crucial in fields ranging from hydrodynamics to marine engineering.