ANSWER

HTML tags are used to annotate a document, such as a webpage, in order to define its structure.  HTML tags define various types of webpage content in terms of headings, paragraphs, lists, tables, data, quotes, and more.

HTML and Cascading Style Sheets (CSS) are almost always used hand in hand.  While HTML defines the structure of a document, CSSs define the presentation of a document.  Using the HTML <style> tag, a predefined style from a CSS can be referenced to format the content of the HTML document as desired.  Using HTML and CSS together allows for the decoupling of the structure and presentation of a document.  One of the benefits of this is that the presentation of a document can be changed at any time without modifying the HTML document itself.