The advantages of OLED displays are extensive- colours are bold and vibrant, blacks are completely black, the screen can be curved. This makes OLED a brilliantm piece of technology for creating phones. Unfortunately, OLED cells can deteriorate over time, which leads to burning on the screen. "Burning" is just a nickname for when the cells lose some of there accuracy and become faded or dull compared to the other cells. This primarily happens with permanent hud items, like the bluetooth symbol at the top of the screen, or the battery icon