I/O modules are devices that are used to read analog or digital values from sensors and other devices. These modules can be used to control lights, motors, and valves or for communication purposes. They are often used as an interface between two different systems or components. They can also be used to store data and to provide control inputs to a system. There are different types of I/O modules, such as analog input/output modules, digital input/output modules, and interfacing modules. Analog input/output modules allow data to be read from analog sources such as voltage, temperature, and pressure while digital input/output modules allow data to be read from digital sources such as switches and binary values. Interfacing modules are used to connect different systems together and to allow them to communicate with each other.