720p
720p is a progressive HD signal format with 720 horizontal lines/1280 columns and an aspect ratio of 16:9, normally known as widescreen HD. All major HD broadcasting standards include a 720p format, which has a resolution of 1280×720.
The number 720 stands for the 720 horizontal scan lines of image display resolution. The p stands for progressive scan, i.e. non-interlaced. When broadcast at 60 frames per second, 720p features the highest temporal resolution possible under the ATSC and DVB standards. The term assumes a widescreen aspect ratio of 16:9, thus implying a resolution of 1280×720 px.
720i is an erroneous term found in numerous sources and publications. Typically, it is a typographical error in which the author is referring to the 720p HDTV format. However, in some cases it is incorrectly presented as an actual alternative format to 720p. No proposed or existing broadcast standard permits 720 interlaced lines in a video frame at any frame rate.