help me to make a pid temprature

Hello,

i want to make a pid to control temprature to a small box using a resistor (i saw someone use a resistor 10ohm 5 watt) for heating and he use the PWM signal and 12V to power by it. and also i will enter the value of Kp,Ki and Kd using a clavier

but i didn't understand the relation between the signal and temperature ?
and what is the maximal temperature could this resistor reach it

i wish you help me with any infos and thank you (and sorry for my bad english)

PLEASE ANYONE CAN HELP ME

Connect your resistor to your 12V supply and measure the temperature. That will be your maximum.