Pseudo-class (CSS)

In Cascading Style Sheets, a pseudo-class is a keyword added to selectors that specifies a special state of the element to be selected.

Description

For example :hover will apply a style when the user hovers over the element specified by the selector.

Pseudo-classes, together with pseudo-elements, let you apply a style to an element in relation to external factors, including:

The history of the navigator (:visited, for example)
The status of its content (like :checked on some form elements)
The position of the mouse (like :hover which lets you know if the mouse is over an element or not)