The SmartThings platform was updated with Matter support back in October, with Samsung rolling out Matter integration to SmartThings hubs last year. With the app update, Matter-enabled smart home devices that are connected to a SmartThings hub are able to be controlled with an iPhone, iPad, or Apple Watch.
Prior to now, Matter accessories connected to a SmartThings hub were only able to be controlled with an Android device, but now either Apple or Android devices can be used, which is useful in multi-platform households.
Matter is a smart home standard that is designed to integrate with all major smart home platforms from Apple, Samsung, Google, Amazon, and more. A Matter home accessory can connect to both HomeKit and SmartThings, for example, and as long as an appropriate hub is available, it can be controlled through either smart home platform.