Types of Affordances in UI
Affordances in UI can be classified according to their performance and presentation. Anyway, their main goal is to actualize the knowledge and experience people already have to simplify the interaction flow.
Explicit (Obvious) and Implicit (Hidden) Affordances
Based on their performance, we can find obvious and hidden hints in UI.
Explicit affordances are based on widely known and typical prompts that direct the user to a particular action. For example, when you see a button designed as an obviously clickable element, aka visually similar to the buttons in the physical world, you understand you can click or tap it to interact. If it is supported by a text or icons the affordance becomes even more clear: it informs you what will be the feedback from the system.
Implicit affordances are not that obvious. They are hidden and may be revealed only in a particular flow of users’ actions. The cases when we get tooltips or explanations hovering on a layout element are the ones. Other examples are diverse multilayered elements of navigation such as drop-down menus or expandable buttons that aren’t seen all the time or from the first seconds of interaction but are unveiled after a particular operation. Perhaps, one of the most debatable points here is hamburger menu that hides the access to functionality behind the special icon.