A Den Chief is a Scout, Venturer or Sea Scout assisting a Cub Scout den. But the story is far more important than those words suggest as the Den Chief:
Serves as a Scouting role model for the Cub Scouts in the den, as well as the entire pack;
Promotes Scouting in general and the local troop in particular;
Encourages the transition of Webelos Scouts into Scouts BSA;
Holds a leadership position in the troop or crew, thus fulfilling an advancement requirement in the unit.