Flowers are the reproductive organs of plants. Flowers come in many different shapes and sizes, but all of them contain a few basic parts. These include petals, sepals, stamen, pistil, stigma, ovary and nectary. These parts all play different roles in helping the plant reproduce and make seeds.
The sepals help protect the flower while it develops. It is possible to see the sepals as green "leaves" at the base of the flower. When the plant produces a fruit, the sepals are usually the "leaves" that are at the top of the fruit. The sepals protect the flower and prevent animals from trying to eat the flowers before the plant has produced fruits. The petals help attract pollinators who come in and collect nectar from the nectary. Nectar is sweet and is used as a source of food for many animals. Bees notably use nectar to make honey. Often, flowers have UV guidelines so pollinators can go directly to the nectary and collect nectar.
The stamen consists of a filament and an anther. The anther contains the pollen sacks. When pollinators come and drink the nectar, they get pollen on their bodies, which get transferred to the female parts of another flower. This helps ensure genetic diversity of the plant. Pollen is typically yellow and powdery. Some plants, including certain types of trees do not use pollinators and instead spread their pollen by having wind blow pollen from one flower to another.
The pistil, stamen, and ovaries are known as the "carpel" or female parts of the flower. They eventually produce fruits and receive pollen. The pollen lands on the stamen, and then fertilizes the eggs in the ovaries. The fertilized eggs turn into seeds, while the surrounding ovary turns into a fruit. Most flowers have both male and female parts on the same flower, and have some mechanism to prevent pollen from one flower from fertilizing eggs in the same flower. However, some trees, such as pines, have separate male flowers and female flowers. Big pine cones are female, and the much smaller cones are male.