What is aspect ratio?
In a 2D world, Aspect Ratio is the ratio of width to height of a rectangular object. In the media domain, it can be used for Display, Image and Video sizes.
Representation of aspect ratio
It is expressed in the notion of width:height. For example, an image of 300px x 300px has an aspect ratio of 1:1 and an image with 300px x 150px has an aspect ratio of 2:1.
For a given aspect ratio, there are endless possibilities of sizes.