The designer has a clear conceptual model, of how a product works. But when users interact with a product, designers aren’t present. Users have to get their conceptual model from the product system image. When interacting with a product, we can’t talk to designers to understand their conceptual model. So we rely on whatever information we can find out about the product.>From it’s shape, form, signifiers, affordances. And even instruction manuals. This information combined, is what we call the system image.