Google Play Services is the First Play Store app from Google to cross 5 Billion Downloads

Google Play Services is the first Play Store app to cross 5 billion downloads

GOOGLE PLAY SERVICES: 

GOOGLE HAS just had its first android app to hit 5 billion downloads in the Play Store. Google Play Services was first launched in 2012, and since then, more than 5 billion people have logged into an Android device with their Google account to enable it. 

It's actually an android bloatware that no one has ever downloaded. It doesn't appear in your app list. You can't open it. You can't delete it. even You can't uninstall it, but then nothing else works. It's Google Play Services.