Article I, Section I - All legislative power herein shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives.
This simple sentence describes the very basic structure of the legislative branch of our government, but does not describe the massive amounts of debate and compromise needed to create our government, specifically the legislative branch.
Under the Articles of Confederation there was a unicameral (one house) legislature where the states had equal representation (one vote each). This section of the Constitution creates a bicameral (two house) legislature, named Congress; the two parts being named the House of Representatives and Senate. At the Constitutional convention both ideas were debated. Many wanted to keep the unicameral system with equal representation, known as the New Jersey Plan. The other plan, known as the Virginian Plan, sought to make a bicameral legislature with both houses membership being determined by the population of the state. After much debate (which more of it will be shared in up coming lessons), they compromised on a bicameral legislature. One house's membership would be based on the population of the state (House of Representatives) and the other would be based on upon the idea of equal representation of the states (Senate).
One principle you see in this section of Article I is that of the separation of powers (principle of dividing the powers of government between separate but equal branches). Each branch of the government has specifically defined powers laid out in the Constitution. The specific power given to Congress is legislative power; the power to make laws. One overlooked item in this section is the fact that ALL legislative power is vested in Congress. When a president writes executive orders, or a regulatory commission makes new rules without a law from Congress they are usurping the power given to Congress by the Constitution.
Associated with this is the principle of checks & balances (principle of each branch having a set of checks on the power of the other branches). Since the Congress is a two house legislature that means there is a series of checks and balances on each other so that the House and the Senate do not get more powerful than each other. We will examine these checks and balances over our entire study of the Constitution.
But for today that is all I will discuss. The next lesson will focus on the structure and setup of the U.S. House of Representatives. Any questions? Class dismissed.