The texture should be slightly firm, a distinctive sign of quality mozzarella in Italy. 

There is also the term "fior de latte" (flower of milk) which guarantees a cow's milk mozzarella that has never been frozen.

There's an easy way to know whether you have a true Italian mozzarella:
Cut the ball in half, then pressing lightly with the tip of your knife on a sliced side, you should see a few drops of milk come out of the half ball.
If this is the case, you can be sure you have true mozzarella.

Available in balls, cylinders, sliced, grated. 

If you don't want to use the entire mozzarella ball all at once, you can keep it for several days in an air-tight container covered with liquid (half water, half milk). 

Take the cheese out of the fridge a half hour before using so that it is at room temperature when served.

Cow's milk mozzarella is grated and used on gratins - a major difference between cow's milk and buffalo milk mozzarella. 

In Italy, mozzarella is eaten both hot and cold: in salads, on gratins, on pizzas, bruschetta, pasta, etc.