CSS (Cascading Style Sheets) is a style sheet language used to describe the way of displaying documents written in HTML or XML.

Its main goal is to separate the presentation description from the structure, thanks to that it becomes much clearer. CSS also simplifies the definition of changes depending on the device and its properties, allowing for example to adjust the displayed content to the given resolution.

More info:

• Mozilla: https://developer.mozilla.org/en-US/docs/Web/css
• w3schools: https://www.w3schools.com/css/
• Wikipedia: https://en.wikipedia.org/wiki/HTML