What is the purpose of the 'alt' attribute in an image tag?

The purpose of the 'alt' attribute in an image tag is to provide a description for the image. This is particularly important for accessibility, as it allows screen readers to convey information about the image to visually impaired users. In addition to enhancing accessibility, the 'alt' text serves a functional role in situations where the image fails to load; it gives users an idea of what the image is supposed to represent. This ensures that the content of the web page remains informative and meaningful, even without visual elements.

Setting the image URL is handled by the 'src' attribute, while the 'alt' attribute is not related to image size adjustments or linking images to URLs, which are managed by different attributes.