System identification is about modeling the relationship between inputs and outputs.
G and H can be parameterized in many different ways. These are special techniques for linear difference equations that work for general noise properties. The toolbox uses a least squares technique to find ARX models and an iterative Gauss-Newton minimization procedure for other models. For both state-space and ARX models, powerful tools let you simultaneously inspect many models of different structures and orders. Default choices are displayed and can be automatically selected.