I process my raw files and save as jpg along with the xmp sidecar files. My silly question is how does the jpg file appear if no xmp file accompanies it? Is the xmp just a snapshot of the jpg when it was created from the raw file so it looks like the processed raw file.
I send the jpg as an email attachment and, of course, want it to look like the finished raw file.
The xmp file contains your editing history, it’s not needed to display the exported file.
It is useful if you remove the raw from darktable"s database: using the xmp, you can always reimport it without losing the editing history.
It is also possible to share the xmp with others, to show how you edited the image. This is often done on this forum, either for troubleshooting, or in the PlayRaw category.
When you just export a JPEG, no sidecar file is created, but the metadata is written into the file itself. You can fine tune this in the export properties, e.g. to skip geo data. Only when you import the jpegs afterwards, a xmp will be created.