Buoyancy is the upward force exerted by a fluid on an object immersed in it. It is a result of the difference in pressure between the top and bottom of the object, with the pressure at the bottom being greater due to the weight of the fluid above it. This force is what allows objects to float in water or other fluids. The amount of buoyancy an object experiences depends on its volume, density, and the density of the fluid it is immersed in.