There are many countries in the world in which there is a state religion.  That means the state religion is officially accepted and endorsed by the government.  Any state, which does not have a state religion, is known as a secular state or country.  In the same manner, a country having a state church means that country is following a particular branch of Christian belief.  State religions mean the government has established a religion and given sanction and approval to it.  But on the other hand, it is also possible for a national religion and national church to be established in a country without any government interference and control from the state.
State religions can have government endorsed support and also financial support.  Some state religions allow people of other denominations to practice their fate.  On the other hand, there are countries that do not let any other religious body, which is in competition with them to practice on that land. 

A good example is the antagonism between Catholicism and Protestantism in the 15th century, which caused the Bartholomew massacre, where the Huguenots were killed upon the order of Catherine de Medici, who was a Catholic.  In 1533, Henry VIII broke away from the Roman Church and imposed Protestantism in England.  His daughter, Mary who was a Roman Catholic, persecuted the people who were Protestants, until Elizabeth brought Protestantism and the King of England as the head of the Church back to England.  The Church of Scotland is a National church, which functions without any political interference.

More Pages:

Christian Church

Christian Clergy

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Introduction To Religion

Jesus Christ

National Church

Orthodox Church

Protestant Church

Religion And Politics

Roman Catholic Church

The Bible The Church Architecture

Types Of Religion

Wedding Church Music