Google Play services: Last updated September 26, 2012: Stakes and Opportunities

Delivered by the Google Play Store, Google Play services aims to be is a platform, which offers integration with Google products, such as Google+, in Android apps. 

Therefore, the Google Play services platform consists of a services component that runs on the device and a thin client library that you package with your app. The component is delivered as an APK through the Google Play Store, so updates to Google Play services are not dependent on carrier or OEM system image updates.

In general, devices running Android 2.2 (Froyo) or later that have the Google Play Store receive updates within a few days. This allows you to leverage the newest APIs for Google products and reach most of the devices in the Android ecosystem.

The client library contains the interfaces to call into the services component. It also contains APIs that allow you to resolve any issues at runtime such as a missing, disabled, or out-of-date Google Play services APK. The client library has a light footprint if you use ProGuard as part of your build process, so it won't have an adverse impact on your app's file size. See the Downloading and Configuring the Google Play services SDK for more information on how to configure ProGuard. More! 

(image from developers.google.)