CSS (Cascading Style Sheet) is used to define the presentation or how the web page must look.
Using CSS we can add colors, change font size and even more. It can also be used to define how an web page must adapt to different devices like Mobile, Desktop.
Using CSS we can provide a function or a rule, which can be used in a single web page or for the whole website.
CSS can be provided both within an web page or outside by creating a separate CSS file.
CSS file provides user an easy way to maintain and add new changes to the styles.