Whta is fetilisation and what are the types of fertilisation

The action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote. The gametes that participate in fertilisation of plants are the sperm (male), and the egg cell, and in flowering plants a second fertilisation event involves another sperm cell and the central cell which is a second female gamete. In flowering plants there are two sperm from each pollen grain.