HomeKit is Apple’s standard for controlling devices in your home. It’s a standard, not an App. You can think of it as a little database on your iPhone. Or just structured information.
Homekit contains all your devices. To begin with Apple does not call it devices but accessories. An accessory is typically something you buy in a shop, such as a light or a sensor. In order to use it in HomeKit the accessory has to be certified for HomeKit.
You can recognise Apple HomeKit accessories by this logo:
There are all kinds of HomeKit accessories: Switches, Lights, Window Coverings, Locks, Sensors, Thermostats, Fans, Valves, Bridges, Cameras, Doorbells, Faucets, Garage Doors, Air Conditioners, Air Purifiers, Humidifiers, Outlets, Receivers, Routers, Security, Speakers, Sprinklers, TVs and Windows.
Window Coverings are curtains, (venetian) blinds, roller shutters and the like.
The most well-known accessory is probably Philips Hue. Philips started to support HomeKit very early on and was to many people their first HomeKit product. And Thinka is a HomeKit accessory too.
Thinka is a special kind of HomeKit accessory, just like Philips Hue it is a bridge. Thinka bridges KNX and Z-Wave to HomeKit.
This opens up a whole new range of possibilities for KNX and Z-Wave home owners.
KNX home owners can now use their KNX and Z-Wave devices such as lights, curtains, thermostats, garage doors along with their Philips Hue lights, Sonos, Somfy, Netatmo, HomeKit cameras, Logitech, Danalock door lock, Gardena, Velux, Lutron and Honewell accessories. And more.
All from the Home App and create scenes and automations with all of them.
Or connect their audio/video from Arcam, Bang & Olufsen, Bose, Bowers & Wilkins, Cambridge Audio, Denon, Harman Kardon, JBL, LG, Loxone, Marantz, MOON, NAD, Naim, Onkyo, Pioneer, Revox, Sony and Yamaha.
See more about HomeKit at How To Use HomeKit?