Feedback
Also said as Player feedback, Game response
Any way the game tells you what just happened and how you did: a sound, a number, a flash, a word. It closes the gap between doing something and knowing what it did.
People learn by correcting, and they can only correct what they are told about. Without feedback, a player cannot tell a bad plan from bad luck, and they stop trying to improve.
Say it
“When a shot misses, show where it landed and play a dull thud. Right now the player cannot tell whether they aimed badly or the weapon is random.”
Where you’ve seen it
Dance Dance Revolution judges each step in words, from Perfect to Boo, the moment you make it, so you always know how close you were and which way to adjust.
Not to be confused with juice
Feedback is information: did it work, and how well? Juice is how richly that information is dressed. A plain "12 ms early" is feedback with no juice at all.