Why Do Airplanes Have Tails?

"Plane!"""a word squealed in delight by toddlers who hear, look up, and see a big gray object, a jet, sometimes leaving a billowy trail of white smoke (vapor), flying overhead. What is it? How did it get up there when I am down here? Can you take me to see a real plane? Can I touch it? Can we go inside? Can I ride in one?

The wonders of the airplane never cease to amaze us. Endless questions come f...