In google-maps, you can create your own maps displaying several placemaks with additional information.
You may manually create placemarks in google-maps, but that might be a lot of work, if you have thousands of adresses to be displayed. For example, if you like to show all Fast-Food restaurants in the U.S.A.
geocoordinate & map uses your address lists and saves them as kml-files, which are used by the google-api for displaying the placemakrs in a google-map.

The google-map api only accepts kml-files holding the corrsponding geodata (latitude and longitude) to an address.
Therefore geocoordinate & map first retrieves the corresponding geodata (latitude and longitude) to the addresse also using the google api.
Since geocoordinate & map also exports plain tab-delimited text-files you may use the geo-information in many other navigation software products.