HTML, or HyperText Markup Language, is used by web developers to create web pages. HTML often embeds programming languages and applications making it possible to deliver, access and execute virtually any program via the world wide web.
HTML forms the building blocks of all websites. HTML allows images and objects to be embedded and can be used to create interactive forms. It provides a means to create structured documents by denoting structural semantics for text such as headings (H1, H2, H3), paragraphs, lists, and hyperlinks.
HTML uses tags to communicate to the browser (i.e. Firefox, Chrome, Explorer) how to display text and images. Tags are contained in < > symbols. In most cases you start with the beginning tag, put in the word or words that will be affected by this tag, and at the end of the string of words, you place a closing tag.
When you tell the browser to open a document, it reads the document first, then lets the document dictate how the screen will be filled. When the browser reads the HTML document, it translates that into the beautiful, content rich website you see before you!