HTML (HyperText Markup Language) is the language used to create web pages, while CSS (Cascading Style Sheets) describes how those web pages should appear. For example, HTML will say 'this text should be blue', but CSS will specify how blue it is: maybe it's navy blue or teal or baby blue! CSS can also be used to control where things appear on the page: above each other or below each other; behind each other or in front of each other; etc. This means you can use both HTML and CSS together to create complex layouts with multiple columns, floating images and more! There are many different ways to use CSS within your website project depending on your goals for design/functionality within a given element/area of content on an overall site template design plan. Frontend developers typically work closely with designers during the early stages of product design through wireframing before handing off their UI codebase to another developer responsible for implementing it in a back-end language such as PHP on top of a server stack like LAMP (Linux Apache MySQL PHP), MEAN (MongoDB Express Nodejs Angular Docker), etc. Frontend developers are also responsible for making sure their code is well-organized, efficient, and performs well. They might use tools like Gulp or Webpack to automate tasks like compiling Sass files into CSS or packaging JavaScript modules. Frontend developers also need a thorough understanding of accessibility standards as well as cross-browser compatibility issues such as polyfills or graceful degradationFor example, if you want to add a background color or image behind text in your website design, then you would use CSS. If you want to change the font size and/or color of certain elements within your site template, then again you would use CSS.