Website and technology
CSS
Abbreviation for Cascading Style Sheets
In short and in plain language
CSS decides how a web page looks.
It sets colours, fonts and spacing. It also sets where the content goes.
The look is kept apart from the content. So the page can fit the screen. It can also fit your needs, for example a larger font.
Definition
CSS defines how a web page looks: colours, fonts, spacing and the arrangement of the content. Because the design is kept separate from the content, a page can adapt to the screen size and to visitor settings, such as a larger font.