Short for Picture Element, a pixel is a single point in a graphic image.

 The width of the screen to the height of the screen is the aspect ratio.   It describes the shape of the rectangle of the space. 


Pixel aspect ratio (often abbreviated PAR) is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel.




 Aspect Ratio Rectangles fit within an outer rectangle with an aspect ratio of 1.78:1 and all of them also covered a smaller common inner rectangle with the same aspect ratio 1.78:1.[4] The geometric mean of the extreme Aspect Ratios, 4:3 (1.33:1) and 2.35:1, is also 1.77:1.


The Aspect Ratio is the relationship between the width and height.   A Ratio of 1.33:1 or 4:3 means that for every 4 units wide it is 3 units high (4 / 3 = 1.33).   


Currently there are five common Aspect Ratios. These are 4:3, 3:2, 16:9, 1.85:1, and 2.39:1.