please explain clausius inequality

the Clausius inequality, or "inequality of Clausius", refers to the argument that when a body is taken from an initial state, e.g. state one, to a final state, e.g. state two, and then back again to its initial state, the entropy S added to the body S1 will not equal the entropy removed from the body S2. In other words, S1 and S2 will be not be equal and will thus be unequal.

this is all about the clausius inequality