what is the significance of the titles under the user names and how are they obtained?
It's based on how many time you posted, ask questions and given answers.
"The Autodesk Expert Elite program", it's not an application, they refer to it as a "program" but it's not something you need to install or require any sort of application.
Your title is just based off what you contribute to the forums here and if you make it that far, there is the "Expert Elite" group or status that someone would contact you about joining.
There is nothing you can do to alter that title I am aware of other than just participate here as you normally would.
They are based on total participation in the community and they will change the more a person uses the community in different way's.
You can read more about the Expert Elite program by following the link in my signature
Thanks
Discussion_Admin
Edit: Please note ranks are not just volume based.