What is the profile plugin?
From Joomla! Documentation
The printable version is no longer supported and may have rendering errors. Please update your browser bookmarks and please use the default browser print function instead.
This article is for Joomla! CMS Version(s) 
The profile plugin makes it possible to add extra fields to the user profile form in 4 places:
- The registration form
- The frontend profile editing view
- The backend profile editing view (My Profile)
- The backend user manager user edit view.
Each of these are controlled independently. They can all be the same or specific fields can be available in each form. Similarly, fields can be set as required independently for each form or all can be the same.
Any field type from the form library can be used.
Optionally the profile for a linked user can be displayed in linked content record.
Multiple profile plugins may be used.
See Creating a profile plugin for more details.