In constitutional monarchy a country is ruled by a king or a queen but the country has a constitution which the king follows.
Example: Until quite recently, Nepal was monarchy. The previous constitution of Nepal, which had been adopted in 1990, reflected the fact that the final authority rested with the king. A people’s movement in Nepal fought for several decades to establish democracy and in 2006 they finally succeeded in putting an end to the powers of the king. Now the people have to write a new constitution to establish Nepal as a democracy. The reason that they do not want to continue with the previous constitution is because it does not reflect the ideals of the country that they want Nepal to be, and that they have fought for.