Both LTE-M and NB-IoT were developed by the 3GPP to address the growing need for wireless IoT (Internet of Things) devices, which need to consume as little power as possible, operate in remote areas, and are typically only sending a few bytes at a time.
LTE CAT-M1 (abbreviated LTE-M) is based on the existing cellular LTE framework your mobile phone uses, modified to serve low power IoT applications. For this reason, LTE-M is the dominant wireless IoT platform used in countries that have widely available existing LTE networks such as the U.S., Brazil, and Germany.
NB-IoT (Narrow Band IoT) is based on older GSM and CDMA technology and attempts to use large open sections on those spectrums. NB-IoT is being rolled out in countries that don’t have much LTE coverage and where GSM and CDMA are still popular, such as India, China, and South Africa.
