Aerospace engineers design, analyze, model, simulate, and test aircraft, spacecraft, satellites, missiles, and rockets. Aerospace technology also extends to many other applications of objects moving within gases or liquids.
Examples are golf balls, high-speed trains, hydrofoil ships, or tall buildings in the wind.
Aerospace engineers are typically specialists in fields with fancy names such as aerodynamics, propulsion, navigation, flight testing, and more. You can learn a lot more about aerospace engineers from the American Institute of Aeronautical and Astronautical Engineers . The U.S. Government Bureau of Labor Statistics has a nice description of aerospace engineers and also provides a job outlook.