a civil war

     A civil war means citizens of the same country are fighting each other ( instead of fighting people from another country ). When citizens fight to overthrow their own government, it is called a revolution. When they fight with each other, it is called a civil war. A civil war sometimes happens after a revolution, when the citizens fight over what kind of a new government they should  have.
     You may be familiar with the American Civil War, in which one part of the United States ( the North, along with the federal government ) fought the other part of the United States ( the South, with a new government they had made ). The people in the South didn't want to be part of the United States any longer--they wanted their own country.
    Other countries have had civil wars,  for different reasons, and with different histories. England had a civil war. China and Russia each had one. So did Ireland.
     If you want to know more about America's civil war, you can look for an old miniseries that was shown on PBS, called "The Civil War".