An alt tag, also known as an alt attribute or alternative text, is an HTML attribute used to provide search engines with a textual description of an image on a web page.
Modern content management systems (CMSs) like WordPress provide a blank field on each web page for users to enter alt text: a brief textual description of images on a page. (There is one blank field for each image.) Alt text helps search engines understand and rank images for relevant queries.
Once alt text is added, the CMS automatically wraps the text with the HTML code (alt attribute), helping search engines find and process that alt text.
Alt text and alt tags are part of image SEO.