For $X_j$'s : $log(X_1)\sim N(0,1),log(X_2)\sim N(0,\sigma^2)$

I'm trying to calculate $\rho_{max}$ and $\rho_{min}$ for $\rho (X_1,X_2)$. One step in the given solution I have is:

$\rho_{max}=\rho (exp(Z),exp(\sigma Z))$ and $\rho_{min}=\rho (exp(Z),exp(-\sigma Z))$

but they've made some references to comonotonicity and countercomonotonicity. I was hoping someone help me understand how they're relevant. (I know how to get this from the general expression but want to know specifically what the comonotonicity parts were saying.)