When you are creating a presentation, you can add speaker notes that you can refer to later while delivering the slide show to an audience. During your presentation, the speaker notes are visible on your monitor, but aren't visible to the audience.
Add notes while creating your presentation
Type your speaker notes in the Notes pane below each slide. If you don’t see the Notes pane, click Notes on the task bar at the bottom of the slide window.
If your notes exceed the allotted length of the Notes pane, a vertical scroll bar appears on the side of the pane. In PowerPoint 2013 and PowerPoint 2016, you can also enlarge the Notes pane by pointing your mouse at the top line of the pane and then dragging upward after the pointer turns into a double-headed arrow. (In PowerPoint Online, the size of the Notes pane can't be changed.)
What the notes look like in Presenter view
In Presenter view, you can see your notes as you present, while the audience sees only your slides: