Zigbee is a low-power wireless mesh protocol built on the IEEE 802.15.4 standard, most often operating at 2.4 GHz. It suits battery sensors, switches and smart devices, forms mesh routes through powered nodes, and needs a coordinator or hub to manage the network.
Zigbee and Z-Wave solve a similar problem in different bands. Zigbee shares 2.4 GHz with Wi-Fi, which makes channel planning matter, and it answers that with mesh routing and low duty cycles.
Mesh and coordination
A coordinator forms the network, routers extend it and end devices sleep between reports. Removing a powered router can break a route that other devices were relying on.
Coexisting with Wi-Fi
Zigbee channels sit between Wi-Fi channels, so choosing both carefully limits collisions. Interoperability improved under Zigbee 3.0, though pairing across vendors still warrants testing before specifying it for a building.