Unlike civilians, whose jobs are either full-time or part-time, members of the armed forces break down into two major classes of work classifications. Those classifications are active duty and reserve duty.
Active Duty Military
Anyone who is considered on active duty is in the military full time. They may or may not live on a military base, and can be deployed at any time. People who have chosen to enlist as active duty service members, have full-time jobs. Active duty also includes members of the Reserve Components on full-time training duty, but it does not include full-time National Guard duty. Being on active duty in the Army, for example, means that soldiers serve 24 hours a day, seven days a week for the length of their service commitment minus time off and vacations. However, if the job requires 24 hours of straight work, that is what gets done. Service terms usually last between two and six years, depending on the unit and its mission.
Reserve Duty Military
Persons in the Reserve or National Guard are not full-time active duty military personnel, although they can be deployed at any time should the need arise, while reserve duty is more similar to a part-time job that enables you to keep your civilian career while you continue to train near home.
A military reserve force is an organization composed of citizens who combine a military role or career with a civilian career. Their main role is to be available to fight when their military requires additional manpower. Reserve forces are typically considered part of a permanent body of armed forces. By having reserve forces, our nation can reduce its peacetime military expenditures while maintaining a force prepared for war.