A computer monitor is an output device that displays information. The display in modern monitors is typically a liquid crystal display (LCD) with LED backlighting. Older monitors used a cathode ray tube (CRT). Some Monitors are connected to the computer/PC with a VGA, Digital Visual Interface (DVI), HDMI, DisplayPort, Thunderbolt, low-voltage differential signaling (LVDS) or other connectors and signals. Originally, computer monitors were used for data processing while television sets were used for entertainment. From the 1980s onwards, computers and their monitors have been used for both data processing and entertainment, while televisions have implemented some computer functionality. The common aspect ratio of televisions, and computer monitors, has changed from 4:3 to 16:10, to 16:9. Modern computer monitors are easily interchangeable with conventional television sets and vice versa. However, as computer monitors do not necessarily include integrated speakers nor TV tuners (such as Digital television adapters), it may not be possible to use a computer monitor as a TV set without external components.
OLED Organic light-emitting diodes (OLED) within monitors provide higher contrast and better viewing angles than LCD monitors, but OLED monitors require more power when displaying documents with white or bright backgrounds and have a severe problem known as burn-in, though burn-in within OLED monitors happens rarely. LCD Liquid crystal display (LCD) technology within monitors works by blocking light (glare). An LCD monitor is made of two pieces of special glass that are polarized (this glass is also called substrate) that contain a liquid crystal material between them. A backlight creates light that passes through the first substrate. LCD monitors are currently more common and are used more than OLED, even though OLED monitors emit more light and color.