What is the purpose of hotter/colder plugs in NA applications?

[jday240]

I was looking over the capacities chart at 240sx.org for a 1990 KA24E and noticed that there are three different spark plug numbers: one cold, one stock, and one hot. My question, how would a hotter or colder plug affect performance in my NA KA24E? Please explain this is a new concept that I would like to know more about.
Modified by jday240 at 3:04 PM 10/28/2004

[navysnail]

you only change the plugs if somthing is wrong. use a hotter colder plug if its fouling and a colder if its burning them