What Is CSS?

CSS stands for "Cascading Style Sheets". It is the style language used to lay out web pages, style them and control their visual design. It is used together with HTML (Hypertext Markup Language) to define how a page looks.

CSS is designed to control the appearance of text, images, backgrounds, spacing, colours and every other element on a page. This lets developers manage the structure of a page (HTML) and its style (CSS) separately, so design and content are easier to maintain.

The main jobs of CSS are:

1. Colour and background: Setting visual properties such as the colours and background colours of elements.
2. Typography: Setting the typographic properties of text — font family, size, colour and other text styles.
3. Position and size: Controlling where elements are placed and how big they are.
4. Spacing and layout: Defining the space between and around elements and the overall layout.
5. Animations and transitions: Controlling transitions and animations of elements on the page.

CSS can live in an external stylesheet or inside the HTML file. An external stylesheet lets every page of a website share the same rules and update them in one place, which makes maintenance easier and keeps the look consistent.