The Comments Pane gives you a centralized place to see and organize all of your annotations. It lists each comment, its type, reviewer name, date added, and the text included in any pop-up notes and text boxes.
This pane is a content-aware element, and its tab is visible in the side-bar only if the PDF document contains comments, or you add Notes, text or other markup.
For more information, see Manage and view comments.