Camera dead zone
Also said as Camera window, Camera trap
A box around the middle of the screen in which the player can move without the camera moving at all. The camera only follows once they push against the edge of the box.
Small movements should not shift the entire world. A locked camera makes tiny corrections feel like an earthquake.
Say it
“Use a camera window 160 px wide centred on screen. The player can wander inside it and the camera will not move.”
Where you’ve seen it
Most 2D platformers use one, from Super Mario Bros. on. Itay Keren's essay Scroll Back catalogues dozens of variations.
Not to be confused with stick dead zone
Same words, different thing. A stick dead zone ignores small movements of an analogue stick. A camera dead zone ignores small movements of the player.