...And What You Don't

The display property can also be used to ‘hide’ elements. At first, it may seem difficult to understand why it would be useful to hide an element, but this is done often in order to create “drop-down menus” or “hidden tips” type content.

To hide an element, set the display properties value to none. To get it to appear, you create a selector made up of the parent container and element in question, with the :hover pseudo-class added to the parent.

.child-class-to-unhide {
    display: none;
.parent-container:hover .child-class-to-unhide {
    display: block;