Army National Guard is Different than Army Reserve
Sometimes people confuse the Army National Guard with the Army Reserve. They are both reserve components, meaning they are both part-time soldiers. What does it mean to be a part-time soldier? Typically, both Army National Guard and Army Reserve soldiers serve one weekend a month plus two weeks during the summer within a year (after initial soldier trainings).
But, however, although the Army National Guard and Army Reserve are both part-time soldiers, the Army National Guard and the Army Reserve serve different purpose. The Army Reserve's purpose is to support the active component of the U.S. Army, so doesn't have combat MOS's (Military Occupational Specialty), such as Infantry, Armor (the soldiers who fight on tanks), and Field Artillery. And just as the Army Reserve's job is to support the active component of the Army, similarily, the Navy, Air Force, and Marines have their support counterparts: the Nave Reserve, the Air Force Reserve, and Marines Reserve.
But the Army National Guard have all the combat MOS's the active component of the Army has, doing the cool Army stuff you see in the movies.
Army National Guard Serve Both the Country and a State
When a man or woman joins the Army National Guard, he/she makes an oath to both the President of the United States and the Governor of the state he/she is from. Take a look at the National Guard Oath of service below:
" I, (NAME), do solemnly swear (or affirm) that I will support and defend the Constitution of the United States and the State of (STATE NAME) against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; and that I will obey the orders of the President of the United States and the Governor of (STATE NAME) and the orders of the officers appointed over me, according to law and regulations. So help me God. "