Slide notes are a convenient way to prepare scripts for recording audio or video narrations for your presentation. You can add them to slides in PowerPoint, but sometimes it's more convenient to edit them right in the narration editor.
When you open the narration editor, slide notes are dispalyed in the left part of the screen. You can edit them right in the Notes pane.
If you don't need notes, you can close the Notes pane. You can always enable the Notes pane by selecting the Show notes checkbox on the View tab.
When you click Save and Close, all the changes you've made to your slide notes will be saved to the presentation.