Transit NXT: what are the extensions *.BAS and *.RSA and *.MTX? | I should be more specific ;-)

Forum: Transit support
Topic: Transit NXT: what are the extensions *.BAS and *.RSA and *.MTX?
Poster: Campman
Post title: I should be more specific ;-)

Thank you for your replies, but a general explanation of the extensions doesn't tell me how theses files relate to Transit NXT.

In other words: what do they DO in Transit NXT? What is their function in Transit NXT? Why are there files with a video extension (*.MTS, recognized by Windows as AVCHD Video files) or audio extension (*.MTX if that would indeed refer to Mad Tracker Audio Tracker) in Transit NXT?
I don't use video, I don't use audio in Transit. I don't perform internet searches from within Transit... .

*.BAS and *.MTX come with every Project I create (besides the "language pair files", the files with the language extensions) in the formats
TRAN4"Language Code".BAS
TRAN4"Language Code".MTX
STRCT4"Language Code".MTX.

I also find
TRAN4"Language Code".SUB.

Squires already explained that this *.SUB is a temporary file, but if it is temporary, why is it still there?

The first "Projects" I created in Transit NXT were all put in one & the same folder. I want to split them up in separate folders. But because I can't tell which file belongs to which translation / language pair, I don't know what/how to split them up.