Setting up the relation between an input and an output is basically very simple. There are only about three steps to be done to define that for example a certain light is switched on/off by means of a certain (momentary) push button on the wall:
Another very powerful relation can be the control of a number of outputs (loads) by only one button. This seems more complex, but you can define the relation between the button and the different outputs in only three steps.
All relations which are defined between the inputs and the outputs are always based on one of the two flow diagrams above. It is the functionality of the chosen relation (sometimes this can be more than one function) between the inputs and the outputs which may increase the level of complexity of your work.