CSS before and after pseudo-elements are used to insert content in an element. The end result will appear like it is in the DOM. pseudo-elements are used to style selectors with certain conditions. Also Read- 3D cards in CSS What are pseudo-elements? Pseudo-elements are useful when you want to style a selector with a certain condition. E.g.- when you want to style, the first letter of an element. Some pseudo-elements are ::before, and ::after.