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.

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Source: https://play.google.com/store/apps/details?id=com.google.android.gms