Affordance is what an object or environment lets you do, and how it signals that. The term comes from J. J. Gibson’s ecological psychology (The Ecological Approach to Visual Perception, 1979), where an affordance is an action the environment offers; Donald Norman brought it into design in The Design of Everyday Things (1988; revised and expanded 2013). A door handle affords pulling; a flat plate affords pushing. In games, affordances guide player behaviour without tutorial text: a glowing object affords interaction; a narrow ledge affords jumping; a brightly lit doorway affords movement forward. Well-designed affordances allow players to understand a new environment through observation rather than instruction (course lecture series, see source-player-psychology-lectures).
Norman later separated affordances (the actions that are possible) from signifiers (the perceivable cues that show them), because designers had started using “affordance” to mean the cue. In a game, the climbable ledge is the affordance; the yellow paint or worn edge that tells you it’s climbable is the signifier. Affordances can be visual, auditory, spatial, or learned from convention (red barrels explode).
Affordances operate alongside other player-guidance techniques (colour, lighting, audio cues) to form the implicit communication layer of level design.
Related: ui-design, player-guidance, level-design, game-feel, signifier