The Google Play services subsystem is used by many Google apps, like the Play Store, for example, as well as other third-party applications. It serves as a middle ground and enhances the user experience on Android with Google's online services. Here you can check out our full coverage of the Google Play services Beta for Android, including valuable information about becoming a beta tester.
App Description from Google Play
Google Play services is used to update Google apps and apps from Google Play.
This component provides core functionality like authentication to your Google services, synchronized contacts, access to all the latest user privacy settings, and higher quality, lower-powered location based services.
Google Play services also enhances your app experience. It speeds up offline searches, provides more immersive maps, and improves gaming experiences.
Apps may not work if you uninstall Google Play services.