Hover over text and see a difference

Sometimes you want your button or element or div to change after someone hovers over it with a mouse or anything else. Here is one example of the right of the syntax you can wright in css

By adding the :hover on CSS id, class, or any other identity after the person hovers on it would change based on the new standards given to it.
.id_1:hover {
background-color: blue;
}