What are input/output systems? What are input/output modules?

I/O systems and I/O modules: I/O stands for input/output, and an I/O module is a device that connects networks, sensors, controllers, actuators, and other devices or transmitters and communicate measurements about the state of a process. If I/O modules include intelligence (a logic device), they are considered smart modules. I/O modules are often described by their function, such as digital or analog, and by the quantities of input or output points they can accommodate. Collectively, the modules, connections and networking integration and logic are the I/O system.