Yes, it’s A home automation platform that is built into iOS, so it comes with every iPhone and iPad. You can also add it to a HomePod or Apple TV plus, but you have to have an iPhone to set it up.
Devices are made by other companies and certified to be compatible with HomeKit. They will have a HomeKit logo if they work with HomeKit.
Set up is very easy and you use the Apple home app as your dashboard.
There’s an article in the community created wiki on devices that work with both HomeKit and smartthings. 
http://thingsthataresmart.wiki/index.php?title=Devices_that_Work_with_HomeKit_and_SmartThings
If you want to set up your own server device, there’s also an open source integration called “homebridge“ which let you bring in otherwise incompatible Devices into HomeKit. A lot of community members are using that to integrate smartthings and Homekit.
But you will have to have an iPhone to get started. I don’t think it’s worth it to buy an iPhone just to get homekit, but if you already use one, it’s an interesting platform.