HTML Part 1

HTML (Hyper Text Markup Language) is a type (and most common) of markup language. A markup language is a set of markup tags used to define a document to be rendered by a Web browser. NOTE: HTML is not a programming language.
HTML tags are keywords in angular brackets <> that come in pairs. The fist of the pair is called the opening or start tag. The second is called the closing or end tag. The end tag always has a forward slash / before it.
Example: <opening tag> </closing tag>
HTML elements are everything between the opening and closing tag including the tag itself.
Example: <opening tag> Content</closing tag>
The compilation of HTML elements used in different ways makes up an HTML document. The HTML document is then interpreted by a Web Browser (e.g. Google Chrome, Internet Explorer, Mozilla Firefox, e.t.c) into visual and audio content that is understood by the browser.
In other words, the web browser does not display the HTML tags itself but the interpretation.

Brief History of HTML
(Just for knowing sake

So it is not that compulsory)
HTML was developed by Tim Berners Lee in 1991. It underwent several modifications into HTML+, HTML 2.0, HTML 3.2, HTML 4.01, HTML 1.0 and (most recently) HTML 5.
HTML standards are maintained by the W3C (World Wide Web Consortium)