The meaning of "adopted"

Mommy, he said, what does "adopted" mean?

Well, I said, sometimes a mother and a father cannot take care of their baby and give him or her up for adoption. And then there are other parents who would love to raise another child in their family. Because every child deserves a family! You know that, don't you?

He nodded seriously.

Can we go to South Africa and visit my African mother and father?

Sure we can. When you are just a little bit older, daddy and I would love to go to Africa with you and try to find your African parents.

Yes, I'd like that. I'll go to South Africa and visit my African mommy and daddy.

And then we will go back home again, mommy?

I smiled.

Yes, then we will go back home again.