In theory it does all of below:

• App Scanning: It automatically scans all apps on your device—regardless of where they were downloaded (though it focuses heavily on apps from the Google Play Store and those sideloaded).
• Real-time Protection: It runs safety checks on apps before you download them from the Play Store.
• Periodic Device Scan: It periodically scans your device for Potentially Harmful Applications (PHAs), which are sometimes called malware.
• Warnings and Removal: If it finds a potentially harmful app, it will warn you, disable the app, or in some cases, remove the app automatically.