Which equation is solved with ThermalModel?

With the PDE toolbox, equations of the general form m∂2u∂t2+d∂u∂t−∇·(c∇u)+au=f can be solved. On the other side, I can use the Thermal model object which seems to be very comfortable for solving the heat equation. However, it's not clearly defined what the parameters stand for. For example, what is 'HeatFlux'? Is it the variable g in the generalized Neumann boundary condition n · (c∇u)+qu=g? Isn't there a complete documentation? How can I be sure that the correct problem is solved, when I cannot see the underlying equations?