The Google Maps API gives developers access to the wealth of data and features that Google has available via their maps service. You can request data regarding map data, street view, and places.
Google Maps also provides web-based services such as returning the directions between different locations.
The terms of service are located here https://developers.google.com/maps/terms
These terms of service are additionally governed by Google's terms of service which can be located here https://developers.google.com/site-terms