The answers given by others seem to be pretty on spot OP , but for the sake of additional information I'll throw a few more tidbits in .
To my understanding Amlas was a duchy (
https://books.google.hu/books?id=wjd...0amlas&f=false ) much like Fagaras that existed as a sort of vassal state of the Kingdom of Hungary .
The Banate of Severin (
https://alchetron.com/Banate-of-Severin ) is another polity that seems to have had similar status to these two duchies , with a very explicit frontier march aspect to it , what with it having been given to the Knights Hospitallers by Béla IV with the intention of them guarding it against foreign excursions IIRC .
I must say that the history of what's commonly referred to as Transylvania is a very fascinating subject , which is precisely why it's a pity that a large amount of historical sources concerning it are either unavailable in the English language and/or biased in favor of particular schools of historical thought .
Anyways I hope this post has been of some help to you and I may post some more historical sources if I manage to dig them up .