Explain the concept of popular sovereignty

After thousands of years of civilization, people realized that the notion of social classes was wrong. The reign of incompetent rulers now and then demonstrated that people in the lower and upper classes could behave pretty much the same. Also, the nobility, supposed to hold the responsibility of political power in exchange of protecting the commoners was nearly always neglected as to justify the nobles' privileges and superior social position. The short-lived Athenian democracy revolved in the minds of countless people throughout the years and inspired the modern democracies of today via the works of the Enlightenment free-thinkers who rejected the traditional hierarchical differences between individuals and advocated for a government of citizens that would serve society, not themselves. As the dissatisfaction of the colonists of the Thirteen British Colonies in America with the despotic impositions of the British government grew, a clear idea of a government serving the will of the people emerged, and that thought was best expressed by Lincoln's statement honoring the sacrifice of the Union soldiers at the Battle of Gettysburg: "A government of the people, for the people, and by the people."

In summary, popular sovereignty consists of a government supported by a Constitution and institutions listening to the needs and concerns of the people in order to act in consequence, this is, real democracy in action.