how can estimate Garch model Residual?

Question

I have two questions about the garch model and I need your help. Please help me if possible. I need to answer these questions

1. Does the "infer" command in MATLAB estimate the variance for the garch model? I do not understand the meaning of inference

2. Does not residual mean the difference in estimating the variance and the correct value? So why is it calculated by the following equation? What does res mean in the following relation?

enter code hereestimated_model = garch(p,q) enter code herev = infer(estimated_model,data) enter code hereres = (data-offset)/v

These relationships are provided in MATLAB Help for the "infer" command. But I do not understand them.

Thank you for your kindness.