The definition of IoT (Internet of Things) can be elusive as it encapsulates a large variety of industries and use cases. For the purpose of this article, we will consider any type of device that generates any type of data via sensors that needs to be transmitted over the Internet as IoT. Other than rare cases, the IoT device may not have a direct Internet connectivity, but rather will connect locally to a gateway device that does connect to the Internet and as the name suggests acts as the IoT gateway.
In the most generic scenario, many IoT devices may be connected locally to a single (or few) IoT gateways. This reduces the cost of Internet connectivity per IoT sensor, where otherwise having WAN (Wide Area Network) connectivity on every IoT sensor may not be practically possible or affordable.