Affordness are the the perceived and actual properties of an artefact, which determine how it might possibly be used.
Appearance indicates how to use something:
- A chair affords (suggests) sitting.
- Knobs are for turning.
- Slots are for inserting things.
- A button affords pushing.
- A menu affords choosing.
When affordness are taken advantage of, the user knows what to do just by looking.
When simple things need pictures, labels, or instructions, the design has failed!