HTML - Hypertext Markup Language is the standard markup language for creating web applications.
Hypertext is simply a piece of text that works as a link.
Markup Language is a way of writing layout information within documents. Another way, It is a system for annotating a document in a way that is syntactically distinguishable from the text. Basically an HTML document is a plain text file that contains text and nothing else.
When a browser opens an HTML file, the browser will look for HTML codes in the text and use them to change the layout, insert images, or create links to other pages. Since HTML documents are just text files they can be written in even the simplest text editor.
Semantics - One important aspect in HTML creation is to give text meaning (also known as semantics), so that the browser knows how to display it correctly. The term "semantics" is, that words can be manipulated to influence human thought and action. Lets look at how to use HTML to break a block of text up into a structure of headings and paragraphs, add emphasis/importance to words, create lists, and more.