Alt text, or alternative text, is a written description of an image that is used in digital content. It helps visually impaired users understand the content of images through screen readers. Additionally, alt text improves search engine optimization (SEO) by providing context to search engines about the image. When creating alt text, it should be concise and descriptive, typically no longer than 125 characters. It should convey the essential information about the image, such as the subject and any relevant details. Properly written alt text enhances accessibility for users with disabilities and contributes to a more inclusive web experience.