What does Keynes’s “camera decision” mean, and why is it called a camera?

Discretionary decision-making means that when the government is conducting demand management, it can flexibly decide and choose which policy measure or measures should be adopted based on market conditions and the characteristics of various regulatory measures.

Because when we use a camera to take pictures, the camera is just a tool. The choice of the camera is your choice. The camera is a part of your body.