User Notes is a way to keep tabs on what users are what in the administrator end of a Joomla website. As a site gets larger and larger and more members and administrators work on a site, it is sometimes hard to keep track of all these users and their roles for the website.
User notes is a friendly little reminder to website administrators as to who is who and who does what.
Further more, categories can be setup to help group these notes together in cases where there are large amounts of notes.
User Notes is a great new feature that has been added to Joomla 2.5 to help manage all those administrators and registered users that have accounts on your Joomla website.
In large websites with hundreds of user accounts it is sometimes hard to remember, over a period of time, who is who and what role each user may have on the website.