The Army Reserve is for soldiers who are retiring(Must be an NCO to officially retire) or who are starting off in the Reserve until they can switch to Active Duty or the regular Army group. Basicly used for soldiers who know they aren't going to be active enough based on active duty requirements. Joining the Reserve could be a good way for a soldier to keep their rank,come to watch training everyone in a while, and all over still have a presence in the Army after retiring other than just leaving and becoming a civilian.