The bald-faced hornet is actually a yellowjacket.
A fertilized queen overwinters in some protected place, and then starts making a papery nest out of her saliva and chewed up wood. The first workers hatched continue the work of building the nest, collect food, feed larvae, and protect the nest. Most of the colony dies off for winter, except for the fertilized queen.
The whole time I watched this nest, there was one hornet stationed at the entrance, like a gatekeeper, or a security guard.