You use Ladder Logic to write your project application. Ladder is based on Boolean principals and follows IEC 1131-3 conventions.
Ladder Diagrams are composed of different types of contact, coil and function block elements. These elements are placed in nets.
In any Ladder Diagram, the contacts represent input conditions. They lead power from the left rail to the right rail. Coils represent output instructions. In order for output coils to be activated, the logical state of the contacts must allow the power to flow through the net to the coil.