When two or more people are involved in designing a presentation, there needs to be a channel for feedback. The Comments option works great for this purpose since it allows feedback without actually editing the slides themselves. A comment is a note that can be attached to any slide object or to a whole slide. You can add comments to write important notes for particular slide objects or for the slides themselves. This is a great way to provide feedback. Once a comment is added, you can edit the comment.
Learn how to add, edit, or delete Comments in PowerPoint 2010 for Windows.

