"Alt" is short for alternative, and in the context of the text, it typically refers to alternative text or alt text. Alt text is a small piece of text that describes an image, graphic, or other visual media on a webpage.
It is intended to provide a text equivalent of the information that is presented visually and to make the content accessible to users who are visually impaired or who are using assistive technologies such as screen readers. The alt text comes in handy if the image cannot be loaded.