TM, I could add a brief discussion of swept wings just to make things more interesting.
Swept wings (as used on modern airliners) help to delay the onsite of local shock waves (transonic drag) in 2 ways.
First, to the airflow passing over the wing, the wing appears to have a greater cord than it actually does, since the air passes over it at an angle. To the airflow, the airfoil profile appears to be longer and more gradual, thus the changes in speed of the airflow over the wing are not as sharp, delaying the onsite of sonic flow.
Second, the swept wing also contributes to a more gradual change in the area ruling. Going back to the illustration I used earlier, there's a big difference between the entire leading edge of the wing suddenly showing up in the cross section as you move down the fuselage, and the leading edge gradually showing up in the cross section as you move down. The swept wing both enters into the area rule cross section and exits the area rule cross section much more gradually than a straight wing. This more gradual change in cross section contributes to good area ruling and a delay in the onset of sonic flow.