HD, or High Definition, refers to a video or image resolution that has a higher level of detail and clarity than standard definition (SD) resolution. HD video is typically displayed at a resolution of 1280x720 pixels (720p) or 1920x1080 pixels (1080p), and is characterized by its sharp, clear images and smooth motion. HD images and video are becoming increasingly common, and are used in a variety of applications, including television broadcasts, streaming video, and digital cinema. HD is often compared to Ultra HD (UHD), which has an even higher resolution (usually 3840x2160 pixels or higher) and offers even greater detail and clarity.