The monitor is the primary output device — the interface through which all computed information becomes visible. It receives digital pixel data from the GPU, converts it into light at the correct color and intensity for each pixel, and refreshes this display at the panel's native refresh rate. LCD (Liquid Crystal Display) panels — still the majority of monitors — work by shining white light from a backlight (historically CCFL, now universally LED) through multiple layers: a polarizing filter, a liquid crystal cell layer, a color filter array, and a second polarizer. The liquid crystal cells act as electronically controllable shutters. When voltage is applied to a cell, the liquid crystal molecules rotate, changing the polarization of light passing through and thus controlling how much light passes through the second polarizer. Subpixels (red, green, blue) are individually controlled, mixing to produce the target color. OLED (Organic Light-Emitting Diode) panels are fundamentally different: each pixel contains organic compounds that emit light directly when current passes through them. No backlight is needed. This enables true per-pixel dimming — any pixel can be turned completely off, producing absolute black and infinite contrast ratio. OLED response time is measured in microseconds (compared to milliseconds for LCD), virtually eliminating motion blur. The main historical limitation — burn-in from static content — has been substantially mitigated in modern OLED panels through pixel-shift, logo dimming, and warranty protection programs. Refresh rate (Hz) determines how many unique frames the display can show per second. At 60Hz, a new frame appears every 16.7ms. At 144Hz, every 6.9ms. At 360Hz, every 2.8ms. Higher refresh rates reduce perceived motion blur and stutter because the time between frames decreases. Adaptive sync (G-Sync, FreeSync) synchronizes the display refresh rate to the GPU frame rate, eliminating tearing without adding the input latency of traditional V-Sync. HDR (High Dynamic Range) requires both a bright backlight/emissive layer and a wide color gamut. DisplayHDR 400 certification requires only 400 nits peak brightness — barely distinguishable from SDR. True HDR requires DisplayHDR 1000 or higher (1000 nits), or OLED with infinite contrast. HDR content is mastered at 1000–4000 nits; displaying it accurately on a 400-nit monitor requires aggressive tone mapping that loses highlight detail.