Can anyone explain in simple words what is parametric and nonparametric models are?
A parametric model contains information like dimensions, constraints, and relationships between various entities like edges, sketches and features. You can easily make changes to the design, and it updates and responds to those changes.
A non-parametric model does not contain such relationships. It is essentially a "dumb model" which often happens when a CAD model is imported from another program.
Dumb models can be modified, but they do not have the additional constraints and relationships to allow the update to affect other design elements.