Matter is a manufacturer-independent connection standard for smart home devices. It was developed by leading providers such as Apple, Google, Amazon, Samsung SmartThings and the Zigbee Alliance, which have joined forces to form the Connectivity Standards Alliance (CSA).
Matter is an overarching smart home standard for previously common protocols and connection types in the smart home sector, such as ZigBee, Z-Wave, Thread or WLAN. However, Matter does not replace the existing protocols, but makes them capable of communicating with each other - in other words, it teaches them a common language on the software side, so to speak.