In schematic design, what is the purpose of using a black box?

In schematic design, a black box serves the purpose of representing complex internal functions or systems without detailing the internal components and their interactions. It allows designers to abstractly show how different parts of a system interact without overwhelming the schematic with intricate details, which can complicate understanding and readability. By using a black box, the designer can effectively communicate that there are processes happening internally that aren't necessary to illustrate for the current design context. This is particularly useful when dealing with well-defined modules or systems whose inner workings are understood to be complex but whose exact details are not crucial for the purpose of the schematic.