That list the different type of contents which are allowed to stand in an Html document ^^
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(based on the @Muhammad Umar answer... I have answered by thinking this was the asker posting context of its question :P)
I do not understand your letter and language, but I see that you are a good person. I understand that part in English. Thanks for the help. Hello from Serbia. Where do you come from and what kind of letter I would like to know.
Metadata: Content that sets up the presentation or behavior of the rest of the content. These elements are found in the head of the document.
Elements: <base>, <link>, <meta>, <noscript>, <script>, <style>, <title>
Embedded: Content that imports other resources into the document.
Elements: <audio>, <video>, <canvas>, <iframe>, <img>, <math>, <object>, <svg>
Interactive: Content specifically intended for user interaction.
Elements: <a>, <audio>, <video>, <button>, <details>, <embed>, <iframe>, <img>, <input>, <label>, <object>, <select>, <textarea>
Heading: Defines a section header.
Elements: <h1>, <h2>, <h3>, <h4>, <h5>, <h6>, <hgroup>
Phrasing: This model has a number of inline level elements in common with HTML4.
Elements: <img>, <span>, <strong>, <label>, <br />, <small>, <sub>, and more.