Here's a breakdown:

* Embryo Sac: This is the female gametophyte within the ovule of a flowering plant. It contains the egg cell.

* Fertilization: The fusion of male gametes (sperm) from the pollen grain with the female gamete (egg) within the embryo sac.

* Zygote: The single cell resulting from the fusion of the sperm and egg. This zygote will eventually develop into the embryo of the new plant.

Let me know if you have any other questions!