Fertilization refers to the fusion of the male and female gamete to form the zygote.
When the fertilization occurs inside the organism through insemination then it is known as the internal fertilization and when it occurs outside the organism like observed in the amphibians when male and female gametes fuse in the water is known as external fertilization.
Both are different type of fertilization but share a similarity that is the formation of a single cell called the zygote which grows into the embryo by the mitotic division. The embryo later develops into the organism.
