The HTML <track> element is used as a child of the media elements—<audio> and <video>. It lets you specify timed text tracks (or time-based data), for example to automatically handle subtitles. The tracks are formatted in WebVTT format (.vtt files) — Web Video Text Tracks.
The HTML Underline Element (<u>) renders text with an underline, a line under the baseline of its content.
The HTML Variable Element (<var>) represents a variable in a mathematical expression or a programming context.
The HTML element word break opportunity <wbr> represents a position within text where the browser may optionally break a line, though its line-breaking rules would not otherwise create a break at that location.
The ::marker CSS pseudo-element represents the marker box of a list item (e.g. the bullet point or item number).
The HTML <audio> element is used to embed sound content in documents. It may contain one or more audio sources, represented using the src attribute or the <source> element; the browser will choose the most suitable one.
The HTML <b> Element represents a span of text stylistically different from normal text, without conveying any special importance or relevance. It is typically used for keywords in a summary, product names in a review, or other spans of text whose typical presentation would be boldfaced. Another example of its use is to mark the lead sentence of each paragraph of an article.
The HTML <i> Element represents a range of text that is set off from the normal text for some reason, for example, technical terms, foreign language phrases, or fictional character thoughts. It is typically displayed in italic type.
The HTML element <input> is used to create interactive controls for web-based forms in order to accept data from the user. How an <input> works varies considerably depending on the value of its type attribute.
The HTML <output> element represents the result of a calculation or user action.
The HTML Strikethrough Element (<s>) renders text with a strikethrough, or a line through it. Use the <s> element to represent things that are no longer relevant or no longer accurate. However, <s> is not appropriate when indicating document edits; for that, use the <del> and <ins> elements, as appropriate.
The HTML Small Element (<small>) makes the text font size one size smaller (for example, from large to medium, or from small to x-small) down to the browser's minimum font size.  In HTML5, this element is repurposed to represent side-comments and small print, including copyright and legal text, independent of its styled presentation.
The HTML <span> element is a generic inline container for phrasing content, which does not inherently represent anything. It can be used to group elements for styling purposes (using the class or id attributes), or because they share attribute values, such as lang. It should be used only when no other semantic element is appropriate. <span> is very much like a <div> element, but <div> is a block-level element whereas a <span> is an inline element.
The HTML Strong Element (<strong>) gives text strong importance, and is typically displayed in bold.
Use the  HTML <video> element to embed video content in a document. The video element contains one or more video sources. To specify a video source, use either the src attribute or the <source> element; the browser will choose the most suitable one.