Scamorza is an Italian cow's milk cheese, similar to mozzarella. It can also be made from other milks, but that is less common.
Scamorza can be substituted for mozzarella in most dishes as can any other cheese, but the resulting taste will be much stronger and more dominant. It is reputed to melt better in baking. Using the smoked variety (scamorza affumicata) adds a nice background flavor in replacement of mozzarella.