How to create Google Maps API keys
From JReviews Documentation
Google recently started requiring API keys for displaying the maps on your website. To create the API keys, go to the https://console.developers.google.com.
When you open the Google API Console for the first time, google will automatically create the first "Project" for which you can create the API keys. If you have a single website, you can leave this default project selected and create the API keys for it. If you plan to have multiple websites, it might be a good idea to create a new project, so that each website has its own API keys: