Narrowband Internet of Things abbreviated to NB-IoT is originally an initiative of 3GPP, an international standardization institute that also originally wrote the GSM standards. The intended purpose of NB-IoT is to link battery-powered devices with low data speeds to mobile networks.
There are many geopolitical issues concerning NB-IoT. If you want to read more about this, we refer you to a piece by Nick Hunn, NB-IoT is dead. Long Live NB-IoT. This piece is particularly relevant for devices that are going to be used in the United States.
3GPP has chosen NB-IoT as the worldwide standard for this technology. Since May 2017 T-Mobile has been covering this network in the Netherlands. Vodafone has also started to follow this technology so that you can create worldwide coverage with the choice for an NB-IoT device.
A clear feature of NB-IoT is that you must always connect to a network provider (e.g. Vodafone and T-Mobile). It is not possible to create your own network. This benefits the stability of the application but you are dependent on third parties and therefore also need a SIM card. (embedded SIM is also possible)
Specific features: provider-bound, data roaming possible, data rate approx. 20 kbps (kilo bits per second), number of messages unlimited.