Home Assistant is a platform and hub for smart home devices and services providing local control.
Home Assistant integrates with over a thousand different devices and it allows Users to customise many different operations that can be performed manually or automated to happen.
The Home Assistant OS software image must be downloaded and installed to run in a couple of ways:
Home Assistant Green
This is a gateway device that comes with Home Assistant OS already installed.
There is no wi-fi connectivity with this device.
You could connect a USB Wi-Fi adaptor to it.
Raspberry Pi
Raspberry Pi is a small single board computer developed for teaching computer science.
There are various versions available: latest is Raspberry Pi 5
Comes as a bare pcb only but various plastic cases can be purchased to house it.
Home Assistant OS would need to be downloaded and installed on it.
Please review the attached which explains further regarding this OS.
For Further information on using Home Assistant or setup please refer to their website