Let's start simple - lawn watering.
We can base it on time, say 7:00PM. That's a start but let's not water on Sunday because water is more expensive on weekendss. Let's continue... We can use soil moisture sensor to turn on sprinklers only when needed. You just saved on water and electricity. You also don't have to remember to turn the sprinklers off when it's raining. OK, not bad, let's add a few things... How about using motion sensors to pause sprinklers if someone is about to run into them while watering? We can shut them down and wait 10 minutes to make sure someone is just not standing still, and if there's no motion, continue watering. See that's better.

Time to go to bed. What should happen then?
Probably some lights should be turned off, while some should remain on, and go off at say 2:00AM. Garage doors should close if they are open, but only if nothing's blocking their path.
Alarm system should arm specific zones, or execute "night" routine. Hot water circulation pump should be turned off, and room temperatures be lowered by 2 degrees. We're sure you can come up with a bunch of additional things that fit your routine.
Doable? Sure.
With a press of a single button ...on your smartwatch.

Here comes the hard part...
There are quite a few smart home protocols and standards. Zigbee, Z-Wave, BLE, wifi, etc. So in order to operate all of these devices, they need to be somehow unified at some point. There's a new platform called Matter which supposed to make devices interoperable, but we suspect it will take some time to see that happen, and still smart home devices will have limited functionality when using common platform.
Can we work around these issues and still have coherent smart home environment?
Yes, but...

We need "something" to be a brooker, or a middle-man which will talk to all these systems and platforms behind the scenes in our behalf.
Not only that but will allow interoperability with devices which are not really designed to work tohether with other devices or sensor data, but would be great to integrate, such as robotic vacuum cleaners, heating and A/C units, RFID and others.
For larger smart-home systems, or rather more advanced systems we recommend Home Assistant. It is a control center of your smart home. You manage your devices and add automation there as well.
It can run on a PC or Mac, but we recommend Raspberry pi.
Of course, we can set it all up for you.

Great, so i have my smart home devices all set-up.
My home can make me a coffee and track my pet, but how do i control it all?
And here is where the power of Home Assistand meets our fingers...
We can build custom dashboards for you, which then can be displayed on multipke devices - wall mounted touch enabled tablets, smart phones, acessed through web browsers, etc.
These dasboards allow us to completely tailor the layout functionality, and visials to your specific needs.
We can show you the weather for today or next few days, your calendar events, alarm system status, temperatures, and many, many, many, many more pieces of information. We can also add screen buttons for any function you may need or like to have - lights controll, sprinklers, cameras, vacuum cleaners, washing machines, TV/Audio control and many more. The trick is not to show it all, but to make it just right. Right for you.
We can help with that or do it for you.

And to repeat ourselves agan, we always document our work, so entire smart home environment will be documented as well.
It's great if you remember how it's done, but two years down the road you may forget how something is set-up. Documentation is a key to keep smart home manageable and organized.