Google Play Protect is the company’s comprehensive security suite designed to ensure that every Android device is safe and secure. Announced at Google’s annual developers conference I/O in the year 2017, Google Play Protect automatically scans all apps on Android phones and works to prevent the installation of harmful apps as well as nortifies about harmful urls. It uses machine learning to scan and verify over billions of apps every single day — both inside and outside the Google Play Store. Wondering how outside Play Store? Google Play Protect scans all apps on users Android phones, even those downloaded from outside Play Store, for malicious activity and notifies users it finds something suspicious.
How Google Play Protect works
Google Play Protect checks apps when you install them. It also periodically scans your device. If it finds a potentially harmful app, it might:

How to know if my phone is Play Protect certified
Google Play Protect is on by default, but users can turn it off. For security, Google recommends that users always keep Google Play Protect on. Here’s how you can check the status on their devices:

To sum it, Google Play Protect is the best thing on your Android phone. But yes, it is not perfect and there are chances that some bad apps may slip in so don’t lower your guard completely.