Without a bridge (hub), it will use Bluetooth connection (33ft max distance) and only have ability to control up to 10 lights. And you can't group the lights into zones, and it has basic routines.
With the bridge, it will use Zigby protocol (instead of Bluetooth) and can control up to 50 lights reaching greater than 33ft, so you don't have to be in the same room) and can also allow control from outside the home by enabling remote access.