The document discusses the <img> tag in HTML 5 which is used to embed images on webpages. It describes the img src attribute to specify the image URL, the alt attribute to provide alternative text for accessibility or if images don't load, and the size attribute like width and height to resize images. The document also mentions using the <img> tag inside an <a> tag to make images into clickable links to other webpages for usability and to make the site more interesting.