Unit 7 introduces HTML (Hypertext Markup Language), which is used to structure and present content for the web. HTML has two main components: hypertext, which allows users to navigate between pages by clicking links, and markup, which involves using tags to structure text. Some key advantages of HTML are that it is easy to learn and use, free, supported by most browsers, easy to edit without special tools, and integrates well with other languages. The basic structure of an HTML document involves tags like <html>, <head>, <title>, and <body>. HTML editors can be either text-based or WYSIWYG (What You See Is What You Get) and allow writing and viewing HTML code.