@MassiveSalad22
thermostats. Think of your house heating as being like your oven. If you want it to reach a temperature you put it onto that (say 200) it takes around (say) 15 minutes to heat up, so you turn it on while you're doing prep, then it's ready when you need it.
if it's too hot or too cold for what you want to cook you adjust the temperature & your oven adjusts to get to that temperature, once it's there it stays at that temperature until you turn if off, unless you set a timer or turn it down.
yhermistat for heating is the same. If you want the house to be warm when you get out of bed, you set the timer for half an hour/an hour before you get up, to a temperature you'd like it to be when you get up & the CH will do it's magic & you'll get up to a warm house. But if no one is going to be home you don't really want it heating an empty house so you set the timer to tell the thermostat what time to cool down (I set it for half an hour before I go out as then it's not wasting heat but not does it get too cold again) You can set it for 'off' or a temperature you'd like it to stay at (or FROST*).
then the same routine for the evening, night.
the timer determines how long the boiler/CH spends getting to & remaining at gets to & remains at the temperature you've set the thermostat at.
the reason people set them at different temperature is two fold. One part is that people have different comfort level/draughts/windows etc and different finances! The second part is that people have them in different places in their houses and with different environmental factors (draughts/fireplaces etc).
so 18° in my house won't be the same as 18° in your house. 18° won't be the same if your thermostat is right near your radiator as when it's right near your door.
I've probably just confused you more, it's much easier to explain face to face! 😂😂