Questions about "saving" (work and otherwise)

[ChristopherDrum]

Sorry for the basic question, but I don't see an obvious way to do this.
For context, I'm learning DurexForth and am doing programming examples, tutorials, etc.
In DurexForth, there is a vim clone and I write my program to disk using :w!filename
In the main interface, I can run ls to see what's on disk, and I see my file there.
However, when I quit VirtualC64, I get two strange occurences.

1. I'm asked if I "want to save changes" to VC64 but I have no idea what that means. Does a VC64 document contain a copy of the modified disk image? What "changes" is it prompting me to save?
2. When I launch VC64 again, load in the .d64 image I used previously, and run ls my appended file from earlier is not there.

I see that if I open back up the "saved changes" I'm brought back to the DurexForth program already running. So I guess "saving changes" is... saving state? Am I expected to just keep saving/opening the same state file? At what point will the files I create be written to an actual file so I can use them on another system?