target temp is the temperature fhr heat pump is aiming to produce and will change according to the external temperature and the heating curve
Actual HP temperature is the measured temperature. If it’s not close to the targer, the HP will no doubt adjust the compressor and fan speeds to suit
c1 temperature is the calculated required temperature of the water going into the secondary circuit. It’s a function of your thermostat setting. if you turn up your room thermostat, C1 rises to suit.