The black box is a representation of a system.
No knowledge about the internal workings of the black box is expected. It may not be known, or you may not know it. The system is only known in terms of inputs and associated outputs.
All inputs are not the same. Some inputs control what the system does.
Other inputs control what the system operates on.
The output can be used to drive inputs - this is feedback.
To know the black box is to know the relation between it’s inputs and outputs; to contruct a model of how it might work.
A model may reveal the internal workings of the black box.
Does the black box make you uncomfortable? Does it leave you with the feeling that your knowledge is superficial or incomplete? Do you perhaps seek to know everything? If so, there is one more thing you should know.
All systems have black boxes. Complete knowledge of any system is not possible. Uncovering how a system works - and constructing more models - reveals more black boxes.
Some elements were inspired by https://en.wikipedia.org/wiki/Black_box.