Hover your mouse over any boldface item or link in this example for a couple seconds, and you will see a small tooltip appear.

Wildebeest Wiki

Thye tooltips are created by the title attribute. You have to see the source code to see how that is accomplished.

A Universal Attribute (also called Global Attribute) can be used in ANY HTML element. The title attribute is Universal, so you can create tooltips in any HTML element.

In contrast, MOST attributes are NOT universal. For example, the href attribute is only used in elements such as anchor (a) that reference other documents.

It is common to use tooltips with links like the one in this page to provide more information about the link. But it is not very common to use tooltips like with the boldfaced items in this example. Using it in the body element would be horrible because the whole page would generate a tooltip! Basically, just use your common sense.

Much more elaborate tooltips can be made using CSS/JavaScript. But HTML provides the title attribute as a quick, easy way to provide simple tooltips.