NB-IoT (Narrowband Internet of Things) is a Low Power Wide Area (LPWA) network technology designed for IoT devices to transmit small amounts of data over long distances with low power consumption. NB-IoT was initially designed to leverage existing LTE networks and operate on licensed spectrum. 
NB-IoT is ideal for IoT applications that require long battery life, low data rates, and deep penetration into buildings or underground. It's suitable for smart city applications, smart metering, asset tracking, and remote monitoring, among others.