What is dysfunctional dysphonia?

Hi, I would like to know what is "dysfunctional dysphonia"?
Is it a synonym for "functional voice disorders" or "non organic dysphonia" or some kind of subcategory (hyponym)? I have read a lot about it, but I have great difficulties really understanding what kind of symptoms or complications this disorder includes. They are often talking about psychogenic dysphonia, spasmodic dysphonia or muscle tension dysphonia for example, but I cannot figure out whether they are talking about categories of dysfunctional dysphonia or if it is the same disorder. And as in the literature authors do not really agree with each other about how to define it (eg, are nodules or polyp included), the more I read, the less I understand.
Thank you in advance (and sorry for my English. I am French, I hope I made myself understood clearly).