I took this information from https://en.wikipedia.org/wiki/Zigbee
Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and other low-power low-bandwidth needs, designed for small scale projects which need wireless connection. Hence, Zigbee is a low-power, low data rate, and close proximity (i.e., personal area) wireless ad hoc network. The technology defined by the Zigbee specification is intended to be simpler and less expensive than other wireless personal area networks(WPANs), such as Bluetooth or more general wireless networking such as Wi-Fi.
Applications include wireless light switches, home energy monitors, traffic management systems, and other consumer and industrial equipment that requires short-range low-rate wireless data transfer. Its low power consumption limits transmission distances to 10–100 meters line-of-sight, depending on power output and environmental characteristics.[1] Zigbee devices can transmit data over long distances by passing data through a mesh network of intermediate devices to reach more distant ones. Zigbee is typically used in low data rate applications that require long battery life and secure networking (Zigbee networks are secured by 128 bit symmetric encryption keys.) Zigbee has a defined rate of 250 kbit/s, best suited for intermittent data transmissions from a sensor or input device. Zigbee was conceived in 1998, standardized in 2003, and revised in 2006. The name refers to the waggle dance of honey bees after their return to the beehive.[2]
Zigbee Tecnology compatible with Alexa:
See that videos:
Explaining Wireless Sensor Nodes: Zigbee vs. WiFI
ZigBee Architecture Basics
BLUETOOTH ZIGBEE WIFI explained simple
For my students in Latin America: the teacher is from India speaks English with an accent for what she says slowly and is understood enough, if it still costs them they can place the subtitles in Spanish and they will understand much more..