What is 1280×720 resolution?

720p (1280?720 px; also called HD ready, standard HD or just HD) is a progressive HDTV signal format with 720 horizontal lines/1280 columns and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1). … The p stands for progressive scan, i.e. non-interlaced.