TDK Sample Application: Flux

Hello,

I am a student working on a research project at Dalhousie University. I
have been reverse engineering the sample application that comes with
TDK, since the documentation is horrible.

Is there any flux documentation? 

I understand how actions work, but what is the action of the following
url, located in the flux section of the sample app:

http://localhost:8080/newapp/servlet/newapp/template/user%2CFluxUserForm.vm/username/turbine?mode=modify

Specifically, the encoded url and the "username/turbine" portion. Why
use a comma? Is username a form of mapped action? If so where can this
be set?

Thanks, Chris