Consent of the governed refers to a principle of democracy that states that the sovereignty of the government comes from its people. Therefore, the people are the only ones who can create laws and chose their representatives. Moreover, the government cannot create laws unless these are supported by the people.
This is an important value for the Founding Fathers because they believed that this principle was violated by the King of Great Britain. The Founding Fathers believed that the King had created laws that had not been approved by the people he governed.