Not sure, think that it more a general grease - copper grease is a high temperature anti-seize also often known as copper slip... Bought it at Builders Warehouse in a tub, but can also get it in tubes at Midas.
If you are fitting new pads then look at the old pads to see where their back plates made contact with the calliper and piston, this is where you want to apply a very thin film of copper grease. Of course must not get into contact with the friction material or disk. Use a small amount for the bolt threads holding the calliper onto the calliper bracket etc. Other places in general, hub faces and wheel stud threads.