The term ‘affordance’ is linked to the abilities and functions an object can perform, with an action from a person. As people, we grow up learning and knowing certain visual cues which help us in our daily lives, with mundane things such as opening doors and using equipment. These are all because of the design of these things- a lip on something indicates that we can open it, and a handle being at hand height indicates we should pull it. These are perceived affordances, because based on the information we are given, we are able to deduce what should be done. If you can’t figure out how to use something just by looking, then it’s been badly designed!
For example, in my accomodation, we have fobs instead of keys. Theoretically, these work well, but each one unlocks 3 different locks, and they all respond differently. The first one to get into the main building is a simple swype, and it unlocks. If you hadn’t used it before however, it might be difficult to understand.
The second one is also fairly simple, but so similar to the third one that I mix them up; for both I have to hold the fob against the knob, press it in and twist. But for both i have to twist the opposite way, and one farther than the other. While the visual cues are there, a light which changes colour when my key has been accepted, and a knob that clearly twists, without instruction i would have ended up unable to get into my flat.