Fertilization is the process by which a new individual of the same kind is developed (or born). It differs from pollination, where the pollen is transferred from a male part (anther) to a female part (stigma).
Fertilization takes place in a flower when ripe pollen (from the same type of flower, typically carried by wind or insects) from the anther is transferred to the stigma, threadlike tubes that are generated from the pollen grain. This pollen tube enters the ovule (of the ovary) and releases sperm cells, which fuse with the eggs inside the ovule, leading to fertilization. Once the ovule receives the entire content of the pollen tube, it fertilizes and develops into a seed (encasing the embryo and endosperm in a seed coat).
Note that in flowering plants double fertilization takes place.
Fertilization within plants takes place when haploid gametes come together to produce a diploid zygote which will eventually develop into an embryo. The process occurs when male gametes (pollen grains) are transported by animal or by wind to the female reproductive organ, the ovule (female gamete in gymnosperms or conifers) or the pistil (female gamete in angiosperms or flowering plants). Once together the haploid gametes, the male sperm and the female ovule, fuse and share their genetic material. Once fertilization takes place the embryo develops within the female gametophyte. The newly fertilized embryo becomes the seed. The seed contains the gametophyte tissue (which is used as a food source until the seed has been planted) and an integument or seed coat in order to be able to survive.
Fertilization in plants happens very similarly to fertilization in humans. It occurs with haploid gametes (sex cells such as sperm and egg in humans) meet to form a diploid zygote (an embryo in humans). In plants there is pollen rather than sperm. Pollen is carried on the wind, by animals, through animals etc. Pollen reaches the female sex organs (example on a cone of a needle-leaved tree), fertilizes the egg, and forms a protective seed.
Fertilization takes places in the ovary of the female flower.When a carrying agent like wind/water/animals carry pollen grains from male anthers to the female flower part i.e. stigma, a pollen tube forms and the pollen grain travels down the style and finally reaches the ovary where it fertilizes an ovule.The ovule in the future becomes a seed. This is how fertilization occurs in flowers.
Each ovule must receive the contents of the pollen tube before it can develop into a seed and it usually takes about 3-4 days to reach the ovule.
Please note that there are two types of plants:
1) A monoecious plant which has both male and female flowers
2) A dioecious plant which has either all male flowers or all female flowers.