This might seem like a somewhat unusual question to raise, but it isn't that odd for a person not to be entirely familiar with what the flag symbolizes. The flag is considered a living symbol of the United States of America's history, freedom, and pride. Originally, the flag displayed 13 stars that represented the 13 Colonies. Today, those original 13 Colonies are represented by the stripes; the red stripes symbolize valor and hardiness while the white stripes represent purity. As for the blue background behind the stars, it stands for vigilance, perseverance, and justice. The stars, of course, represent the 50 states themselves.
Due in part to the fact that the American flag is treated as a living symbol, there are very specific rules about displaying the flag (or flags, should you choose to fly multiple American flags).