The tooltip is a common [graphical user interface] element. It is used in conjunction with a [cursor], usually a mouse pointer. The user hovers the cursor over an item, without clicking it, and a small box appears with a name or description of the item being hovered over. A common variant, especially in older software, is displaying a description of the tool in a [status bar], but such descriptions are not usually called tooltips.
A good example of tooltips are the widely used tooltips on web pages. Many graphical [web browsers] display the attribute "title" of an [HTML] element when it is hovered.