OLED—short for Organic Light-Emitting Diode—is a new display technology that differs from traditional LED/LCD TVs in a number of important ways.
First, OLED tech allows a TV's pixels—the individual points of light that make up the picture—to activate independently of one another. The pixels emit their own light and colors, unlike in LED/LCD displays, where a backlight shines through the pixels to create an image.
The ability to turn individual pixels on and off means OLED TVs can offer much higher contrast than traditional LED/LCD TVs. That's because when OLEDs pixels shut off, they are truly black. In contrast, black areas of a picture on an LED/LCD display usually appear as some shade of gray, since there is still light shining through from the backlight.
The removal of the LED backlight has another key benefit, as well: Most OLED TVs are far thinner than their LED/LCD equivalents.
There are only a few drawbacks to OLED TV technology, the most glaring being price. Because the technology is newer, OLED sets are typically more expensive than the non-OLED competition. They also have some eccentricities that LCD TVs don't, such as taking longer to "settle" into calibrated settings, and needing to be shut off periodically to safeguard panel life.