Fertilisation
The joining of a male cell from pollen with an egg cell in the ovule, which starts a seed.
Also: fertilization
Pollination only delivers the pollen. Fertilisation is what follows. The pollen grain grows a fine tube down through the style into the ovary, and a male cell travels along it to join the egg inside an ovule. That ovule becomes a seed, and the ovary around it becomes a fruit. Once a flower is fertilised its petals usually fade fast, since their work is done. This is one reason florists prefer unpollinated flowers.