Devices, Gateways & Services
Most of this documentation talks about "devices". However, what we actually mean is: devices, gateways, and services.
A device, directly connected to Drogue Cloud.
This may be an embedded device, or a more powerfull compute node with a full blown operating system. It may also be a containerized application, running inside an Edge node, connecting to Drogue Cloud.
A device, which acts as a proxy for other devices, that may not directly connect to Drogue Cloud.
This may be some kind of Linux machine, which allows non-IP enabled devices, like Bluetooth Low Energy (BLE) devices, to connect to Drogue Cloud, by forwarding messages between the two protocols.
In some cases a gateway is not a single device, but a bigger, maybe cloud based, service as well. Still it acts as a proxy for devices to communicate with Drogue Cloud.
An example might be "The Things Network" (TTN), or "Sigfox". Both services have their own technical infrastructure to which devices connect. These services act as a proxy to their devices.
From a Drogue Cloud perspective such services are "gateways" as well.
It may be, that between Drogue Cloud and the actual device, additional "gateways", like a LoRaWAN gateway, are in place. A LoRa device might connect to its local gateway, which connects to the TTN network, which then connects to Drogue Cloud.
However, for Drogue Cloud only the device which directly connects (TTN service) and the originating device (the actual device) is important. Intermediate gateways may be in play, but are not relevant.