I understand the conceptual meaning of gauge transformation which "can be broadly defined as any formal, systematic transformation of the potentials that leaves the fields invariant". I understand for example the U(1) and S(3) gauge symmetry in Gauge Theory. But what is this got to do with Coulomb gauge? Please use plain english in explaining and less on math because I'm not good in math but I just want to have general birds' eye view idea of coulomb gauge and how it is related to gauge transformation. Thanks.