To synchronize using Export and Import, you first export the database to a file.
Then you transfer this file to the other device. You can do this with a cabled connection or any other means.
On the other device you can import the file.
This also allows you to export the contents of the database for other purposes.
The exported file is a CSV file commonly used by Excel.
You can also use it to import information from another source, as long as the import file has the same CSV format.
Enter one or two books and export that information to see how the CSV file should be formatted.