What is the Difference Between Similar But Different Things, Terms, and Objects

What is the Difference between Zygote, Blastocyst, Embryo and Fetus

Human beings are made by nature and different genders are made to make sure the survival of the human kind. The natural attraction between the two genders serves as a special factor to gain this goal. This natural attraction helps to bring the two persons closer and thus the aim of the nature for the continuation of human species on planet earth is served well.