Google Play Services allows your phone to benefit from the latest versions of apps without upgrading your Android operating system to the latest version. It doesn't support all applications, but most Google-developed apps like Gmail, Google+, Google Play, Google Maps are supported.
Google Play Services is not the kind of application we usually see. If you open it, nothing will happen or change. However, the app is installed by default on Android devices. It's a package of APIs that make sure fewer apps are dependent on Android operating system updates to run.
Google Play Services is very closely linked to Android system itself, and it runs as a background service in the Android operating system. The APK is offered through the Google Play Store, so updates to it are not dependent on OEM system image updates.
It requires many permissions including access to and control over SMS, access to sensitive log data and all the information of Google applications and more. Android devices older than Android 2.3 cannot enjoy the service of this app.