Aspect ratio refers to the proportional relationship between the width and height of an image, video, or display screen. It is expressed as a ratio of the width to the height.

In simple terms, aspect ratio describes the shape or dimensions of the visual content. It determines how wide or tall the image or video appears. Common aspect ratios are represented by numbers separated by a colon, such as 4:3, 16:9, or 1:1.

For example:

A 4:3 aspect ratio means that the width of the content is four units and the height is three units. This aspect ratio was commonly used by older television screens and standard-definition videos.
A 16:9 aspect ratio means that the width is sixteen units and the height is nine units. This is the standard aspect ratio for modern widescreen displays and high-definition videos.

Aspect ratio is crucial for maintaining the correct proportions of visual content across different devices and platforms. It ensures that images and videos are displayed properly without being stretched or distorted. It is particularly important when dealing with content that will be viewed on various screens, such as televisions, computer monitors, mobile devices, and projectors.

Choosing the appropriate aspect ratio for creating or displaying content depends on the intended use, the medium, and the platform where it will be presented. Different aspect ratios are used for various applications, such as cinema, television, online videos, and social media platforms.