An appliance is an affordance bound to data or application logic. A button by itself is just an affordance but a button with a "Save" label and callback that triggers the save API is an appliance.
A save button inherits all the general affordances given by button (clicking, and a label). But now it performs a specific purpose. We can distinguish a save button from a delete button from a log out button. Each is its own unique appliance.
- Appliances can contain one or many affordances.
- Appliances can be in its own file.
- Appliances can be declared ad-hoc in a structure.
- Appliances cannot fetch data.