The goals of CIT camp programs are to teach the general skills of leadership that can be used at school, home and community (not just at camp.) For camp leaders ages 15-16, the curriculum includes assisting Camp Directors and Counselors by working with younger kids at camp, in addition to community components like volunteering at senior centers or YMCAs.
Counselors-in-Training or "CITs" are the oldest campers who typically want to apply for a job at camp the next summer, maybe as a Jr Counselor or some other supporting role. Therefore, the CIT curriculum includes more specific skills for working with kids and co-workers, and more experience planning and leading activities.
Both programs give kids age-appropriate challenges that build their skills, confidence and capacity for working with people of all ages.