Well, the file format is JSON, and the default location is in the home directory. More precisely, the default directory to keep stores is: $HOME/PyrusticData/shared.
Private stores are still accessible through the command line interface. You will just need to change the current working directory:
As you can see, Shared is great for sharing collections with other software, or just used as a private database. The command line interface makes things more wonderful.
Between us, do you trust the delete feature ? Here is a snippet of the code which shows that the directory to be deleted must have a particular signature, otherwise it will not be deleted: