You set the temperature, as well as control which vents, fan speed, recirulation or fresh air.
If you set the temp for 21dC and it's 30dC out, it will turn on your A/C so that the temperature of the interior drops to your set temperature. If you set to 21dC and it's 10dC out, it'll turn on the heat for you.
It's great for traveling between places of varying temperature - you don't have to keep adjusting. Also, good for when you hop in a vehicle after it's been sitting because you don't have to fiddle with the controls so much.
There's an "econ" button which ensures the A/C won't come on if you don't want it to (at which point it can't cool the interior as effectively in hot weather either, but on days like today which are cool enough to run without A/C but are on the boarderline for the A/C to be working, I set it on Econ).
I like you can decide where the vents should blow versus the computer. It's a useful and not techologically frustrating system.