A hover state (also called a rollover state) is the slight animation that is triggered when a user rolls their cursor over a link. This helps ensure that site visitors know what they can and cannot click on throughout the site. A hover state can be as simple as a button changing colour or as complex as design elements moving or fading in and out.
As a web designer, you should design your websites to give your visitors the greatest ease of use, the best impression and most important of all a welcoming experience.