Trouble understanding the Lorentz dispersion model in CST

I have been trying to understand the Lorentz dispersion model in CST, but the documentation only briefly mentions the model in the material overview. I managed to find a good description of the model in Absorption and scattering of light by small particles by Bohren, but I don't understand how ε static and ε infinite arise in CST. Could someone who has experience with this model or CST explain these parameters or how they are related to the formulation in Bohren. Thanks.