Usually users have to move their files into the Google Drive folder to sync. But that changed with this new feature.
As reported by Engadget, Backup and Sync creates all existing data in computers, folders or various other specific locations, can be monitored and copied into Google Drive.
In addition, the Backup and Sync feature can also be used to monitor and make copies of photos or images. This is similar to the functionality of the Google Photos desktop app.
Thus, users no longer need to download Google Photos and Drive at once. Simply install one Google Drive only to be able to get document and photo sync features.
The plan of Backup and Sync will be launched on 28 June for MacOS and Windows. The initial release was only intended for the general consumer, not yet accessible by Google Drive corporate customers.