Here's a breakdown:

* Gametes: These are specialized sex cells (sperm and egg) that contain half the number of chromosomes as a normal cell.

* Fusion: When a sperm and egg cell combine, their genetic material merges.

* Zygote: This newly formed cell is a single-celled organism with the complete set of chromosomes (half from each parent). The zygote then begins to divide and develop into an embryo.

So, the fusion of gametes is the first step in sexual reproduction, leading to the creation of a new individual.