Google map API key
Greetings from Potenza.
As per Google recent announcement, usage of the Google Maps APIs now requires a key. If you are using the Google Maps API on localhost or your domain was not active prior to June 22nd, 2016, it will require a key going forward. Please see the Google Maps APIs documentation to get a key and add it to your website.
Visit below link and follow the introduction there. and create your API key.
Note: Please add your key beetween = and & sign
Hope this will help.
For more information kindly visit below links. this will help you to know more about API and google map.