The document discusses HTML (Hypertext Markup Language), which is used to describe web pages. HTML uses tags to mark elements like headings, paragraphs, and other content. It is a markup language that allows web browsers to display pages. HTML documents can be created using any basic text editor. Common tags include <h1> for main headings and <p> for paragraphs. Attributes provide extra information for tags, like aligning paragraphs left or right.