Reserve

From dKosopedia

Each military service has a reserve component. These are part-time soldiers who usually serve a weekend a month and two weeks a year in peacetime, and frequently, they are active duty military veterans. In wartime they are called up to active duty. There are several levels of activation within the reverses, with differing readiness requirements and call up priority.

The makeup of the reserve components of the Air Force and the Marines are described expressly in their respective articles.

Unlike the National Guard, the reserves are not subject to the authority of a state governor in peacetime, and so do not mobilize to respond to natural disasters and domestic riots. They are part of the United States armed forces.