As used in this article, unless a different meaning clearly appears from the context: “Joint activity” means a governmental function which is carried out by, performed on behalf of, or contracted for two or more localities within a region and includes present and future activities. “Locality” means all counties, cities and towns within a regional partnership. “Region” means a planning district; however, by agreement of the localities of the planning district, localities which are not part of a planning district may be added to the region if the locality’s governing body by vote agrees to become part of the region. In addition, localities may establish, with the approval of the Department of Housing and Community Development, a different regional configuration, provided that at least one of the localities is a city, if a city exists within the planning district, unless the city voluntarily agrees not to participate. “Regional partnership” means an organization composed of government, business, education and civic leaders approved by the local governing bodies of the region to carry out the provisions of this chapter. The organization may be an existing or newly established regional planning or economic development organization serving the region.