According to the National Archives and Records Administration (NARA), there are six main points of the US Constitution, referred to as the “Six Big Ideas.” They include the following.
Popular sovereignty means that the people are sovereign or ultimately that the government represents the people. This means that the government has authority because the people grant it authority. The Constitution begins with “We the People.” By exercising the right to elect representatives and doing their civic duty by voting, the people are the source of government power.
Related to this is republicanism, which is a model of government that emphasizes that the people—or citizens—participate in order to advance the common good of the republic. This means that people have an obligation to fulfill their civic duty.
Because the US government exists because the people give it power, there is a limited government. The government's powers are limited to those powers the people determine and authorize it to have. The government is not omnipotent. The Constitution outlines the areas over which the government has authority.
Another of the six main ideas is that of separation of powers, which means that the Constitution outlines three main branches of government—the legislative, executive and judicial branches—and allocates various powers among them.
Moreover, through a system of checks and balances, another of the six main points in the Constitution, each of the three branches of government has several constitutional checks to oversee the operations of the other two branches in order to ensure the overall balance of power.
Federalism refers to the division of power of a centralized government and various local governments that are located closer to and presumably better understand the people they serve. This gives local government certain authority to self-govern.