Are you refering to the checkout address validation?
The system uses Google Maps Geocoding api to generate the coordinates from input address, then checks if the coordinates are within any marked delivery areas.
Since the system uses Google Maps Geocoding api to validate the address and get corresponding coordinantes, its best to read more about the Geocoding API and maybe restrict the search query to a specific region or country to improve search results.
https://developers.google.com/maps/documentation/geocoding/intro#geocoding