You can do this with CSS.
Example HTML:
<div id="to-hover">
<div id="to-show"></div>
</div>
Example CSS:
#to-show {
display: none;
}
#to-hover:hover > #to-show {
display: block;
}
You may need to change block to inline or some other value depending on the situation. Also you might need to use a different selector than >
if they divs have a different relationship.