What Is Burn-In?
Burn-in is permanent damage to a display where pixels that have shown the same static content for a long time become dimmer or differently colored than surrounding pixels. It's most common on OLED and plasma panels because each pixel is a separate organic light-emitter that degrades with use. Common culprits: taskbars, news-ticker chyrons, game HUDs, TV channel logos. Modern QD-OLED and WOLED panels are far more resistant than early OLED TVs, but not immune.
Burn-In vs Image Retention
"Image retention" (IR) is temporary — the ghost fades after a few minutes or an hour of normal use. "Burn-in" is permanent — it never fades. This tool can help you tell them apart: run the full color cycle at fullscreen for 10 minutes. If the ghost disappears, it was IR (no real damage). If it's still there after 30 minutes, it's burn-in.
The Scrolling Refresher
Scroll mode displays a moving vertical bar pattern across the whole screen. For OLED panels with mild short-term retention, leaving this running for 4-8 hours exercises every pixel evenly, which can help the dimmer cells "catch up" and reduce the visible ghost. This is essentially what your OLED TV does in its overnight pixel-refresh cycle — but you can force it on-demand through a browser. It won't fix permanent burn-in.