Missing .DB and IDX files in folders

In several folders are MP3Info.DB and MP3Info.DB.IDX missing and in other folders the files are present.
Does somebody knows the cause for this??

TIA
Ridefort

The extensions look like database files and database index files to me.
As MP3tag does not use a database these files have nothing to do with MP3tag.
Investigate on your computer which players you use and whether they create these files.
Also, it could be that you got these files from others when copying music from one pc to another.