The document discusses HTML (Hypertext Markup Language), which is used to define the structure and layout of web pages. HTML uses tags to annotate text and other content for display in a web browser. Some key points covered include: - HTML is a markup language that uses tags like <h1> and <p> to structure headings, paragraphs, and other elements. - Web browsers are used to display HTML documents on different platforms like Windows, Linux, and Mac. - HTML documents can be written using any basic text editor and involve writing opening and closing tags around content. - Common HTML tags were demonstrated like <h1> for main headings and <p> for paragraphs.