Cosmological fluctuations: what is gaussian?

When we are speaking about gaussianity and non-gaussianity in a cosmological context, what is gaussian or non-gaussian in the CMB?

What would a non gaussian CMB look like compared to a gaussian one?

Is it just the profile of every overdensity $\delta = \frac{\rho-\rho_0}{\rho_0}$ which look like a gaussian and not an exponential or a sine?