A computer monitor is an output device that displays information in pictorial form. a monitor usually comprises the visual display, circuitry, casing, and power supply. the display device in modern monitors is typically a thin film transistor liquid crystal display (tft-lcd) with led backlighting having replaced cold-cathode fluorescent lamp (ccfl) backlighting. previous monitors used a cathode ray tube (crt) and some plasma (also called gas-plasma) displays. monitors are connected to the computer via vga, digital visual interface (dvi), hdmi, displayport, usb-c, low-voltage differential signaling (lvds) or other proprietary connectors and signals.