Building block of IoT

Four things form basic building blocks of IoT devices.

Sensor & actuators : Sensor are devices which converts physical parameters like temperature, motion etc. into the electronic signal. Actuators are devices which is a contrast to sensor. It transform electrical signal into physical movement.
Processor : processors are the brain of the IoT system. Their main function is to process the data captured by the sensor.
Gateways : Gateway are responsible for routing the processed data and send it to proper location for its (data) proper utilization.
Applications : Application form another end of an IoT system. Application are essential for proper utilization of all the data collected.