If you’ve been using technology for a while, burn-in is nothing new to you. It occurs when an image stays on-screen long enough to permanently show, even when the image changes. Though some types of displays are more sensitive to burn-in than others, it’s a phenomenon that can happen to almost any display. OLED displays are especially vulnerable.
If you own an Android Wear smartwatch with an OLED display, you might have noticed that the watch face shifts around when in ambient mode, almost always being off-center. This is to prevent the static elements like the numbers and details from permanently burning into the display and is enabled by default on many watches. The first gen Moto 360 did not have this feature enabled, and despite being a regular LCD, suffered from burn-in issues.
It seems Samsung has taken the same route with the Galaxy S8 and Galaxy S8+, though not with the entire display. The new on-screen home button shifts around a little bit to prevent burn-in. Though the home button is always at the bottom when in portrait, you would see it in fullscreen or landscape apps if it burned in, so this is a good decision on Samsung’s part.