What's "tummy" mean? Is this a commonly used term?

Native speaker’s answer
Rebecca
A "tummy" is an informal term for one's stomach or abdomen. Other synonyms include "belly," "tum," or "gut." I'd say "tummy" is common to say. However, it could sometimes be considered childish and is often used with children. Ex: You need to put suncream on your tummy before you go swimming, George. => a direction to a child Ex: Since being pregnant, my tummy's gotten bigger.