Layers of IoT in Networking

Sensors in IoT devices inform the device about some condition, such as temperature, and forward that information to a controller.

The controller tests the information from the sensor against a collection of possible responses, identifies the appropriate response and then tells the device's actuators to do something, such as send an electrical signal to turn off an appliance.  The device is connected to the network, most often the internet, and communicates and collects data from other devices.

There could be hundreds of sensor-controller-actuator processes in a large system of IoT devices.