Alt text, or alternative text, is a written description of an image that is used in digital content. It helps users who are visually impaired understand what the image depicts by providing context and details. Screen readers read this text aloud, making the content more accessible. In addition to aiding accessibility, alt text also improves search engine optimization (SEO) by allowing search engines to index images. This can enhance the visibility of a website. Properly written alt text should be concise, descriptive, and relevant to the surrounding content, ensuring it serves its purpose effectively.