Generally speaking, an IoT system can be described by a three-level model: the “Things”, the communication networks, and the Cloud.
An IoT module is a small electronic device embedded in objects, machines and things that connect to wireless networks and sends and receives data. Sometimes referred to as a “radio chip”, the IoT module contains the same technology and data circuits found in mobile phones but without features like a display or keypad.
The most popular model is the CISCO IoT Reference Model which comes from industry. It is primarily a model from the networking perspective.
The other is the IOT-A family of models which describe the IoT architecture from the functional perspective, or from the object- oriented design perspective.
Another key differentiator of IoT modules is that they provide always on connectivity. This is because IoT applications need to send data automatically, in real time without someone hitting a send button.
In addition, they are engineered for extreme durability and longevity and need to operate continuously for a decade or more to justify the business case and cost of the technology.