In jurisprudence, a natural person is a real human being in contrast to an artificial person, meaning an organization that the law treats for some purposes as if it were a person distinct from its members or owner.
For example, the right to vote is given to natural persons only. That is the case for most of the human rights. Therefore, obviously a corporation cannot hold public office, but it can file a lawsuit.
Although science fiction has long fantasized about the possibility of sentient robots (e.g. androids) living among humans (such as Robin Williams Bicentennial Man), no court has yet dealt with the question of whether such a being would be considered a natural person.