Affordance
Also said as Perceived affordance, Visual language
What an object lets you do, and how plainly it suggests that: a handle invites a pull, a ledge invites a climb. The psychologist James Gibson coined the word, and Don Norman brought it to design.
Players read a game from what things look like before reading any text. When the look and the use agree, nobody needs a tutorial. When they disagree, people push on walls for an hour.
Say it
“Every climbable ledge gets the same worn yellow lip, and nothing else in the game uses that yellow. Players should know where they can go without being told.”
Where you’ve seen it
Mirror's Edge paints the things you can climb and use in bright red against a white city, so you can read your route at a sprint.
Not to be confused with signifier
Strictly, the affordance is what the object can do, and the signifier is the mark that tells you so. Game designers often say affordance for both.