CullAi automatically picks better photos from groups of similar photos and flags them as picked. It considers user configured automation rules and face quality of important people to pick these.

AI Score to Rating mapping

You can change these automation rules in Preferences -> Automation -> Auto Pick Settings. Currently, you can select number of photos to be picked from a group and minimum rating a photo should have to get auto picked. You can disable auto pick by setting number of photos to 0.