Bocconcini cheese is small balls of mozzarella, about the size of chicken eggs (thus another Italian name for these, “uvoa di mozzarella“, or “mozzarella eggs.”)
They are usually sold in tubs, packed in water to keep them fresh.
In Italy, the cheese is often made of buffalo milk.
Bocconcini are usually served fresh as appetizers, and rarely cooked.
Use fresh, for salads, etc. They are often matched with tomatoes, olive oil, and basil.
Bocconcino (or its synonym, bocconcello) means “tidbit” or “morsel” in Italian. Literally, it means “a small mouthful”.