In addition to the tabbed pane for Transcript, tabbed panes for Clips and Summary will appear when those materials are available for a video. Clicking the tabs toggles you between the panes.
You can read a summary or overview of the video, when available, in the Summary pane.
You can see any clips created for the video, including those you create, in the Clips pane. Note that you must be signed in to be able to see your own clips. (See "Creating Clips" section for easy ways to make clips.)