Is a low-power, wide-area network similar to SigFox and LoRa but the difference is that nb-iot is for is from the 3GPP standards org and uses a licenced RF spectrum, compare this to LoRa which is unlicened). As it is licenced it is only available through a Telco/Mobile operators network. It main goal is to improve indoor coverage and support huge number of low throughput devices, so like wearables and smart buildings.
Power consumption is not as good as it is for LoRa which is important for devices that are running on batteries and where a long lifetime is important. This is why LoRa is often a better fit for industrial IoT like manufacturing, mining, etc.
TODO: take a closer look at how nb-iot works.