In this PowerPoint Tutorial video you learn how to display a tooltip in presentation mode when you hover the mouse over an object. A tooltip can be shown for any object in PowerPoint. This is a very helpful feature, since it allows you to display small subtle tooltips within a presentation that can be useful in certain situations.
If you need a less subtle display of Text, I recommend to you the video about displaying a pop-up text in PowerPoint: • How to Display a Popup Text in PowerPoint
Displaying a tooltip is easy, but quite counter-intuitive. You do it by setting a hyperlink for the object you want to display the tooltip. It is also very important that the hyperlink itself points back to the slide with the object or a misclick could "break" your presentation.