Parameter explanation of transfer functions

Hi,

I am using a biquadratic second order transfer function model to describe the relation betweem my input and output. Estimation of this transfer function is based on the tfest method from Matlab for discrete time systems. The transfer function function has the following form: H(s) = (Y(s))/(X(s))= (b0 +b1*z^-1+b2*z^-2)/(1 + a1*z^-1 + a_2*z^-2 ) I am basically interested in finding changes of model parameters between two groups. The differences that I find from the transfer function are: the b-parameters and the steady state gain (SSG) of the model. I want to understand why there is a difference between the two groups when comparing b-parameters and SSG. However, I don't have much knowledge about what does parameters represent.

Does anyone have an idea maybe?