Notes allow Admins to leave comments on Users, Jobs and Lessons. They are only viewable by Administrators with the correct permissions (View Operations), and cannot be viewed by any non-Admin user; notes about a User cannot be viewed by that User; notes about a Lesson cannot be viewed by any Client/Student/Tutor attached to that Lesson - it is purely for the reference of Administrators.
An example of a Job page, with the Notes panel highlighted.
Can I view all of my Notes in one place?
All Notes left by Administrators can be found via People > Notes. This page allows you to filter out your notes via the Filter button - selecting this will open the Filter Notes panel, where you can apply various filters to the Notes list, such as when it was created, who created it, who/what it was attributed to and the text within the Note.
How do I adjust the formatting/styling of a Note?
Notes can be edited in HTML Markdown - read more about that here.