Within each chartered organization, there may be one or more "units". A unit is a group of youth and adults which are collectively designated as a Cub Scout pack, Boy Scout troop, Venturing crew, or Sea Scout ship. Each chartered organization may charter as many units as it wishes, but usually only 3 or 4 (one unit for each program level). The BSA council provides the leader training, inter-unit activities, camping programs, volunteer and professional support, and insurance coverage. Units also create their own activities (such as monthly camping trips, outings, or service projects), and most meet weekly at the place of the chartered organization for youth to learn basic skill development and practice leadership in small groups known as dens and patrols.