Is the attachments are stored outside the database, what happens to the attachments when I duplicate a database?

Do both databases point to the same attachment folder? Then, I imagine, if a user in one database deletes an attachment then a user in the second database will get an error.

If the duplication process also copies the attachment folder then the duplication operation can take some time and take up a lot of space.

If the attachments are outside the database then restoring a database backup could get many errors because of missing attachments. What happens?