evrything you edit in Picapport will be saved into the metadata of the edited picture file.
The database is indexing these metadata to enable quick searches in a bunch of files.
However user tags (don't know if this is the correct wording) are stored in the db. It depends if they are also visible to other Picapport users. These are tags for whichbare not saved into the image and should me used for sorting or temporary stuff (my opinion).
That means you can drop that database and rebuild it whenever you like. If you are unable to see tags, than they are a) not saved correctly while editing or b) user tags stored in that db. Editing the metadata is the killer feature of Picapport 😉