A Brassica plant is fertilized when pollen from another plant is moved to another plant by the wind or a pollinating insect. Once on the flower. the pollen goes to carpel and then to the ovules at the bottom of the flower.
These are the anthers, they are the male part of the flower and they hold the pollen grains, which contain sperm cells.
The male reproductive part of a flower called a stamen has a stalk known as a filament that comes up from the base of the flower and on top of the filament is the anther which releases sperm cells in the form of pollen.
Shown below is the female reproductive part of a flower known as the carpel. The carpel contains a style and on top of the style is a sticky portion that catches pollen known as the stigma.
Inside the bottom of the carpel is the ovary that contains ovules, which are unfertilized eggs which when fertilized produce seeds inside a fruit.