ELI5: Explain Like I'm 5

Aspect ratio

Aspect ratio is a way of describing the shape of something. It is the ratio (or comparison) of two sizes. For example, if something is 16 inches wide and 9 inches high, then its aspect ratio is 16:9. That means it is 16 parts wide and 9 parts high. That shape is called "widescreen" and is used in TV displays and movies!