HTML provides semantic tags that describe the meaning of content on webpages. These tags include <p> for paragraphs, <a> for links, and <h1> for main headings. HTML5 introduced new semantic tags like <section> and <figure> to further reinforce the meaning of different types of content. The Document Object Model (DOM) allows programs to access and manipulate HTML documents and content. Web components use newer technologies like shadow DOM to encapsulate different functional areas and allow reusability on webpages.