The Basics of HTML5
HTML5 is the latest version of HTML and includes some features that are sufficiently novel to extend the technology. These are the audio, video and canvas tags that support embedded sound, video and graphics.
HTML5 regresses slightly from the strict rules of HTML4 in favor of a less formal approach but it is still essentially a dialect of XML and firmly based on the use of XML tags to represent data types. So they can also be described as elements or nodes. These tags are visible in a text editor but hidden when the page is rendered in a browser window.
Many web pages do nothing other than display content in a structured way and although they may have some functionality in the form of hypertext links, they are essentially static presentations. They can become dynamic by adding functionality, or behavior, so that they do something, usually in response to user input. This functionality is provided by a program, which for web pages can be described as a web application. So the web page can be identified as the user interface of a web application.