What is goverment and its Purpose ?

Of course the answer really depends on who you ask and
their perspective.  The term "government" refers to the group of people that exercise
power over a country or other group of people whether by their consent, through a power
they wield, etc.  It can be as large as the huge bureaucracy that comes to exist in most
national governments over time or as small as one person in charge of a club or other
small organization.

Its purpose again will depend on what
it is governing.  In the case of the United States, there are also many perspectives on
what the role of government should be.  Some would argue its main role is to provide for
the national defense.  Others would argue that it should provide for the poor and
provide a social safety net.