What the army do?

Answer 1

the army go around and shoot stuff. The British Army is the best trained in the world and rely on tactics and other such tecnical euipment in order to get the job done, whereas all ofther army forces in any country arent as good
Kill people.
In the United States:

The United States Army is an organization of the Department of Defense whose primary responsibility is the defense of the United States and to project it's power overseas in land-based warfare. This includes infantry, helicopter aviation, artillery, medical support, signals intelligence, and air defense, as well as all support functions associated with those areas.

The United States Army works in a joint environment, meaning it's operations are conducted hand-in-hand with United States Air Force (air power), United States Navy (sea power), United States Marines (amphibious warfare), and United States Coast Guard (United States coastal defense) forces to create the single most powerful military in human history.