What does heterogamy mean?

Heterogamy:

1. Heterogamy simply refers to the distinct gametes.
2. Stevens in the year 1905 is the first who worked on the theory of Heterogamy.
3. It is called Anisogamy.
4. It is a sexual reproduction involving the fusion of different gametes.
5. For example, AB males and CD females are heterogamous sexes.
6. In humans, males are heterogamous (XY) while females are homogamous (XX).