What is Zigbee?
Zigbee is a wireless communication protocol designed specifically for home automation. It is an open standard which means it can be freely used by any brand. It is therefore used by many brands, including Philips Hue, IKEA Home smart and Aqara.
Types of Devices
In a Zigbee network, you can have three different types of devices.
A 'coordinator' is the heart of your Zigbee network and is sometimes called a hub, bridge or gateway. It connects to your network, allowing you to set it up and control it from your smartphone. In a Zigbee network, you always have exactly one 'coordinator'.
A 'router' is a device that can amplify the Zigbee signal. This increases the range of your Zigbee network. Most devices connected to mains power, such as smart switches and smart lamps, are 'routers'.
Most battery-operated devices, such as sensors, are an 'end device'. This is due to them not needing to amplify the Zigbee signal and therefore only needing to wake up when they actually want to do something. This allows an 'end device' to last a long time on a battery.
Zigbee has several advantages over for example Wi-Fi or 433 MHz RF for home automation.
Zigbee is specially designed for home automation and therefore does not need to transmit as much information as, for example, Wi-Fi. Also, an 'end device' can sleep when it is doing nothing. All this together makes Zigbee very energy-efficient.
A Zigbee network is a mesh network. This means that the 'routers' pass on the signal until it reaches the 'coordinator' (or vice versa). This allows Zigbee to have a fairly long range. If a 'router' fails, the devices connected to it will automatically switch to another 'router'.
Unlike, for example, 433 MHz RF, with Zigbee the signal goes both ways. This allows, for example, a smart plug to confirm that it has switched on when you give it that command. In the unlikely event that it has not received that command, it will automatically send that command again due to the lack of confirmation, so you don't have to click again to for example turn on your lamp. This makes Zigbee very reliable.