According to the Constitution of the United States, the federal government is divided into three branches to make sure no individual or group will have too much power:
The responsibility of the Legislative branch is to make laws. This branch has the power to impeach the president and to declare war.
The responsibility of the Executive branch is to carry out laws. This branch has the power to send troops overseas and to veto legislation.
The responsibility of the Judicial branch is to evaluate laws. This branch has the power to overrule decisions made by lower federal courts and rule on court cases that question interpretation of the Constitution.