Google introduces a new concept to the Maps API v3, called "library," is a set of Maps API features that're only loaded when explicitly requested by the application. "By packaging features into a library, we can deliver them to apps that need those features without penalising the loading times of apps that don't," stated Google.
A library has its own child namespace under google.maps, and is a fully supported component of the Maps API.
The first library that "we're launching is the geometry library. The geometry library provides a set of utility functions for performing distance, heading, and area calculations in a spherical geometry, such as on the surface of the Earth, and also provides functions for handling encoded polylines," Google added. To use these functions in your Maps API app you must request the geometry library when loading the API: