Park Rangers perform a wide variety of duties in managing parks, historical sites, and recreational areas. Many wear a prescribed uniform.
Duties
Park Rangers supervise, manage and perform work in the conservation and use of resources in national parks and other federally-managed areas. Park Rangers carry out various tasks associated with forest or structural fire control; protection of property; gathering and dissemination of natural, historical, or scientific information; development of interpretive material for the natural, historical, or cultural features of an era; demonstration of folk art and crafts; enforcement of laws and regulations;
investigation of violations, complaints, trespass/encroachment, and accidents; search and rescue; and management of historical, cultural, and natural resources, such as wildlife, forests, lakeshores, seashores, historic buildings, battlefields, archaeological properties, and recreation areas. They also operate campgrounds, including such tasks as assigning sites, replenishing firewood, performing safety inspections, providing information to visitors, and leading guided tours. Differences in the exact nature of duties depend on the grade of position, the site's size and specific needs.
http://www.nps.gov/personnel/rangers.htm