Back in 2015 Google started to roll out face-grouping in its Photos app, however, the feature didn’t go as far as Europe.
Google Nest Hub is already capable of matching faces uploaded to Google Photos and displaying them on the screen and now the feature is slowly coming to its photos app.
The feature works by scanning all of the photos in your library and then creates a snapshot or ‘model’ of each face so that it can group these similar faces into folders and sub-folders. Google only makes these ‘face groups’ visible to the account holder. The face-grouping is only used as a way to organise your Google Photos library. If you disable this feature it will delete the face groups created.
As noted by 9to5Google On July 4th manual face tagging is also coming.