The Safe Folder option is PIN protected. It is designed for confidential documents, photos and videos. This folder is locked every time the user exits the Google Files app and starts interacting with another app. To access the folder, you need to enter the code each time.
Google believes that the new option will be useful when sharing a smartphone. For example, in a family where parents let their child play with the device.
NIX Solutions notes that the Google Files app can be installed on any Android device, even rather weak ones. It also allows you to free up space on your phone and back up your files to the cloud.