Aspect ratio refers to the proportional relationship between the width and height of an image or screen. It is expressed as two numbers separated by a colon, such as 16:9 or 4:3. This ratio is crucial in determining how images are displayed, affecting everything from the composition of a photograph to the format of a movie. In the realm of digital media, different aspect ratios can create varying visual experiences. For instance, 16:9 is commonly used for widescreen televisions and online videos, while 1:1 is popular for social media platforms like Instagram. Understanding aspect ratio helps creators choose the right format for their intended audience.