This site is created with HTML and SASS. SASS is a CSS preprocessor that needs to be compiled into a CSS file. SASS is a tool that makes writing CSS easier and more powerful. It lets you use variables and nesting. Things you normally can't do in pure CSS. It allows you to keep your code cleaner and more organized. It is especially helpful on larger projects.
When you connect a GitHub repository to Netfily, it watches for any changes made to the repository and automatically builds and deploys your site. There is no need to upload files manually with an FTP. It a great way to keep you site updates with your latest code changes.