HTML is the standard markup language used to create web pages. It uses tags to define headings, paragraphs, links, images, and other content. Web browsers read HTML documents and display them as web pages. Common HTML tags include <h1> for main headings, <p> for paragraphs, <a> for links, <img> for images, and <table> for tables. HTML documents are written using tags that describe and define the document's structure and content.