Archimedes principle states that when a body is immersed partially or completely in a fluid (liquid or gas),it experiences an upthrust or buoyant force that is equal to the weight of the fluid displaced.
In simple words Archimedes principle states that when a body is partially or completely immersed in a fluid,it experiences an apparent loss in weight that is equal to the weight of the fluid displaced by the immersed part of the body.