A CSS pseudo-class is a keyword added to a selector that specifies a special state of the selected element(s).
Ref.: https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-classes
The :hover CSS pseudo-class matches when the user interacts with an element with a pointing device, but does not necessarily activate it.
Ref.: https://developer.mozilla.org/en-US/docs/Web/CSS/:hover