HTML
The language in which all websites and web apps are being presented on the web browsers is HTML. This language is what web browsers read, understand and render. In addition to HTML, web applications usually have dedicated JavaScript and style files.
In the dynamic web applications, HTML representation files are generated dynamically, in most cases by the web server. Web server application is using front end templates and data stored in databases to generate final HTML pages.
Static web applications, do not have the server app side. HTML and all corresponding style and JavaScript files are already created and just served by a web server as they are. This approach allows you to host your web pages on different platforms which support static HTML pages but not server side languages. Examples would be GitHub pages or even DropBox.