Difference between TEMP and TEMP_LOAD Subcase options

HI

I am running a Non Linear Quastatic analysis for an assembly  in which one of the components is heat assembled .

To Represent the pre thermal stresses i have given TREF  and A value in the MAT1 of the heat assembled component,and applied a temperature(TEMP card) for the same component .

For the remaining all bodies i have given A=0.and temperature is applied with TEMPD.

Now i want to know how can i combine TEMP and TEMPD to be  able applied for a subcase .

and i am confused between TEMP and TEMP_LOAD. 

can any one please helpme in this.