What is the key concept of democracy?

One theory holds that democracy requires three fundamental principles: upward control (sovereignty residing at the lowest levels of authority) political equality

Answer: The Key Concept of democracy is that the people have the power

Explanation: Republics and democracies are very similar in their governing types, and have one main aspect that is the same; people have the power. For example, while someone has control in a democracy, such as a president or prime minister, people vote in who is going to control their laws. Another side of democracy is that rulers can never have complete authority, and can never have a dictatorship, due to laws in effect to protect said democratic nation.