A more thorough explanation:

A biological child is a child who is genetically related to their parents, as opposed to an adopted child. This term is also known as a natural child.

For example, if a woman gives birth to a child, that child is her biological child. Similarly, if a man fathers a child, that child is his biological child.

This term is important in legal and medical contexts, as genetic relationships can impact inheritance, medical conditions, and other factors.