On the nature of government, few in history have really hit the nail on the head better than the late, great Austrian, Ludwig von Mises:
The government says to the citizen, Pay taxes or my armed constables will imprison you.
A state or a government is an apparatus of coercion and compulsion. Within the territory that it controls, it prevents all agencies, except those that it expressly authorizes to do so, from resorting to violent action.
A government has the power to enforce its commands by beating people into submission or by threatening them with such action. An institution that lacks this power is never called a government.