Basically it will use JS to submit this data to your back-end, where you will grab the requests, process and save the data in DB using your ActiveRecords. After that, you will respond with the updates on the screen.
Hi Bruno, thanks a lot for your quick and very helpful answer!
The link you recommended was 100% what I was looking for and without you I would have never found it. After creating the countries-database I used model generator and CRUD generator for countries. After replacing all content from CountriesController.php, index.php and _form.php from linked source “Create Countries” does what I was looking for. THANK YOU!