Title: It displays the title of the knowledge piece saved.
Tags: It displays the tags assigned to that particular knowledge piece
Mark Completed: Click this option to archive a knowledge piece that is consumed. It would still be saved in the repository but won't be visible by default. This would put more focus on the knowledge elements yet to be consumed. In case, it required to refer back to this information, it would be visible if "All Content" switch is enabled in the search bar.
Edit: All content elements including its visibility can be edited from here.
Comments: Have a focussed discussion with your knowledge buddies or add comments like introduction, summary, notes, or key takeaways on the saved content