Look at the overall schematic of hydronic piping schematics as a group of subassemblies, each of which accomplished a specific (but limited) task.
Years ago in high school shop class, I remember being shown the schematic of a radio. Spread out over the large sheet of paper were hundreds of neatly drawn symbols for components like resistors, capacitors and transistors. All woven together into a web so seemingly complex that it amazed me that anyone could actually have thought it all out. It looked like a giant maze. How could the electrons possibly know where to go much less how fast to go there, and how to oscillate back and forth in such complex ways?
In the days that followed, my shop teacher patiently explained the radio schematic as a collection of “stages.” He drew dividing lines through the complex web and explained how the components in one stage collectively functioned to provide power for the entire system, how another stage provided the proper oscillating frequency that tunes the radio to a given station, and still another amplified the signal strength to drive the speakers. Each subassembly received some kind of input signal, did something to that signal, then passed it along to the next stage.