Ok, I will try again. Maybe it will become clear. Thank you for your help and patience.
I think I know where your question is coming from.
The inputs are grouped together and isolated from the outputs in the physical wiring.
Often, this is done with separate modules with signal counts of 4, 8, 16 and 32 most commonly. There are specialty modules with both inputs and outputs for some models. This is especially true with analog.
You can get modules for nearly any control application voltage and a wide range of current carrying capacity.
In addition to the comments above (especially understanding the scan cycle), think of relay ladder logic in a PLC, just like you would if you had relays with a virtually infinite number of "contacts". These contacts are not really contacts, they are references toa "bit box", they are best read as questions..."If" and "If Not", the bit instructions that pass logic are simply saying if the address holds a 1 or not.
Am I warm?
And going further anyway, when designing your first program, start with a written plan, and start writing the program starting with the outputs and work your way back, by inserting things that must be "true" or "on" or contain a "1" before that output device is energized.