chief executive
the role the president plays when executing, or carrying out, the nation's laws
commander in chief
the role the president plays when ordering troops into action and calling them back home
foreign policy
a nation's plans and procedures for dealing with other countries
diplomacy
the art of negotiating with foreign governments
chief of state
the role the president plays when acting as the symbolic figurehead of the United States
succession
the process of succeeding, or coming after someone