Lots of things can be hooked up through it. One of the biggest things I find I like about it is the way you can merge ecosystems with it.

At home with HA I have an LG TV, Philips Hue lights, a Tapo vacuum cleaner, my EV charger, my own home made solar hot water system controller, a presence sensor that also does CO2 and temperature, a hot tub, and a few other bits and pieces. All of which can be viewed and controlled in the one interface, not the 6 or 7 apps that every individual device wants me to install.

But automations and notifications are the big thing. The presence sensor in the living room turns off the tv if nobody is in front of it for more than an hour. The EV charger tells me when the car is charged. An hour before sunset the light in my living room slowly dims on, and dims off after 9pm when the presence sensor says there's nobody around. When my solar hot water system is a bit slow to heat up on a cloudy day, I get an email telling me to turn the electric booster on (and off when the water's hot). Every Tuesday and Thursday evening the vacuum cleaner is set to clean the living areas, but it doesn't if someone is watching tv, as detected by the presence sensor and the television.

I also don't have to get off the couch to turn on a light, but the idea is that you set up automations that do all the button-pressing for you.