Inactive: flow temperature is based on desired room temperature and outdoor temperature. The actual room temperature is ignored, so heat curve needs to be spot on.
Active: flow temperature is based on desired room temp, actual room temp, and outdoor temp. So if room is colder than desired the flow temp will boost a little bit, if room over heats then flow temp will decrease a little bit.
Expanded: same as active, except the room controller also acts as a room stat, if the temperature goes over desired room temp the heating will be shut down until the room cools a bit.
Easy way to do it for boilers is turn on adaptive heat curve & set to expanded, let the control adjust itself through the winter, you just tell it what temp you want room to be. Have a reasonable setback, ie 16-17 overnight so it's not working too hard bringing house back up to temperature.
I have 20 when it's on 18.5 when off. Sometimes I just leave it at 19.5 24/7.