A shaft is like a long, straight stick that helps things move or turn. Imagine a shaft as a spine for machines. Just like your spine helps you stand up and move, a shaft helps machines do their work. In a car, the shaft helps the wheels turn so the car can go fast or slow.
Think of a shaft as a bridge that connects two parts. When you spin one end of the bridge, the other end spins too. This is how a shaft helps things like fans or merry-go-rounds spin around.
Another way to see a shaft is as a tunnel for energy. Picture a tunnel that lets a train go through. The shaft is like that tunnel, but instead of trains, it lets energy move from one place to another. In a windmill, the wind pushes the blades, and the shaft helps turn that power into energy we can use.
Finally, a shaft can be like a puppet string. When you pull the string, the puppet moves. The shaft is like that string, helping parts of a machine move together in harmony.