A correspondence course for everyone who has completed a basic course as required by a majority of states, or police firearms training, but wants to learn more about carrying a handgun for self-defense and how to enhance one's ability to survive.
Training required by some states or conducted by instructors in all states covers just the basics.
It's almost a sure bet you were not trained in how to expect the unexpected, develop intuition, tactics of confrontation, and how to survive the aftermath of a shooting in which you were involved. These are all subjects that enhance your survivability but are probably not part of basic civilian training. Even police officers need reminders. An advanced course in concealed handgun carry for civilians. Delves deeper into attitudes you may encounter, spotting others who are armed, enhancing your own ability to avoid surprise and being taken unaware.