What does it mean to be adopted?

A first grade teacher was discussing a picture of a family. One little boy in the picture had different colored hair than the other family members. One of the teacher’s students suggested that he was adopted.

A little girl said, “I know all about adoption. I was adopted.”

“What does it mean to be adopted?” asked another child.

“It means,” said the girl, “that you grew in your mommy’s heart instead of her tummy.”