Supervisors know everything.  They have the answers or can find the answers when customers call or when employees need help.  
Supervisors are leaders.  They are always looking to help out.  They coach, they guide, they redirect, they train and they educate.  They make other people better.  They are always looking for better ways to serve the public and to help everyone around them get better at providing the best service possible.  Supervisors are "people" people who know a lot about technology, buses, vans, cars, schedules, web sites, phone systems, training, leadership, and compassion for others.  Supervisors are the go to people that everyone wants to go to for help and support.