The capabilities and responsibilities of Reserve Police Officers vary significantly from city-to-city, state-to-state. Some departments use Reserve Officers like grown-up
Explorer Scouts. Other departments use Reserve Police Officers to supplement their full-time Licensed Police Officers.
Departments that fear the liability of volunteers usually use unarmed civilian volunteers with no police powers. Wearing a police uniform, complete with a badge, these Reserve Police Officers are used for special occasions like parades and city festivals. Some are allowed to patrol (without making traffic stops) to assist stalled motorists and help little old ladies across the street. These unarmed police look alikes are often referred to as "Targets" by Licensed Police Officers because the reservist looks like a police officer but could not fight back if shot at by someone who doesn't care for the police. Self defense training varies by Police Department. Although the reservist isn't carrying a firearm, some are allowed to carry collapsable batons, propelled chemical irritant and handcuffs. The level of support Reserve Police Officers are allowed to give to their departments really varies. Some reserve programs are considered an asset to the department, others a nuisance.
Smaller departments with smaller rosters of Licensed Police Officers often use a reserve program to supplement their regular officers. Given full arrest powers, these Reserve Police Officers wear identical uniforms as the Licensed Police Officers and fulfill the duties of a regular officer. These reservists have to walk the fine line of assisting their community and not taking police jobs away from those who want to be in law enforcement as a career. They also have to worry about taking overtime opportunities away from Licensed Police Officers.
Reserve Police Officers generally are volunteers who have some sort of interest in law enforcement. Many use Reserve Police Officer programs as a way to gain experience while attending school to become a Licensed Police Officer, although there are many who join Reserve Programs based solely on having an interest in law enforcement and giving back to their community while also enjoying the career they already have. Being a volunteer, they receive little or no financial compensation from the Police Department. For many Reserve Police Officers, participating becomes rather expensive when paying for uniforms, duty gear and sometimes a firearm out of pocket.
This writeup is based on personal experience in the United States of America.