1080p is the shorthand identification for a category of HDTV video modes. The number 1080 represents 1,080 lines of vertical resolution (1,080 horizontal scan lines),[1] while the letter p stands for progressive scan (meaning the image is not interlaced). The term usually assumes a widescreen aspect ratio of 16:9, implying a horizontal resolution of 1920 pixels. This creates a frame resolution of 1920×1080. The frame rate can be either implied by the context or specified after the letter p (or i), such as 1080p30, meaning 30 progressive frames per second, or 1080i60, meaning 60 interlaced fields per second.
A 1080p picture, with a resolution similar to that of 2K digital cinema technology, is sometimes referred to in marketing materials as "Complete High-Definition".
Use of 1080p and the closely related 1080i labels in consumer products may refer to a range of capabilities. For example, video equipment that upscales to 1080p takes lower resolution material and reformats it for a higher resolution display. The image that results will not attain comparable resolution to native 1080p source material on a native 1080p-capable display. Similarly, equipment capable of displaying both 720p and 1080i may in fact not have the capability to display 1080p or 1080i material at full resolution. It is common for this material to be downscaled to the native capability of the equipment. The term "native 1080p-capable" is sometimes used to refer to equipment capable of rendering 1080p fully.
Source :
http://en.wikipedia.org/wiki/1080p
