Secularism, also called Secularity, is the idea of something being not religious or not connected to a church. An example of this is the government, which is independent of any religion in many states. In some countries, such as Pakistan, UK, Greece, Iran or Saudi Arabia, there is a state religion. In that case, the government follows the state religion. In contrast, India, South Africa and the United States had founding fathers who made a law that religion and government should stay separate.
In a theocracy the priests of religion are the rulers of the country.