HTML tags are the foundation of the HTML language. Tags are used to distinguish between the beginning and end of elements in the markup. Each HTML document consists of a tree of HTML
elements and text. Each HTML element is identified by a start (opening) and end (closing) tag. The opening and closing tags contain the tag name.

 All HTML elements are divided into five types:
  1. Empty elements - <area>, <base>, <br>, <col>, <embed>, <hr>, <img>, <input>, <link>, <menuitem>, <meta>, <param> , <source>, <track>, <wbr>
  2. elements with unformatted text - <script>, <style>;
  3. elements that display unformatted text - <textarea>, <title>;
  4. Elements from another namespace - MathML and SVG;
  5. ordinary elements - all other elements.


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