You know how a rocket works. You point it where you want it to go, light the fuse and stand back. If it's a big rocket, you stand farther back.
You know what a rocket is good for. It moves stuff really fast, around the world or into space. It burns lots of fuel and money in the process.
You know that a rocket would be helpful if you wanted to put a satellite in orbit or explore the planets.
You know to hire a rocket scientist when it's time to design your rocket and plan the flight to take a specific load to a specific point in space.
What else do you need to know?
Don't let the underlying complexity of something useful stand in the way of learning its value. You don't have to know how to build it to understand how to use it.
Photo by Steve Jurvetson.