Flowering plants actually are the youngest group in the plant world, a group referred to as angiosperms. The main feature that sets angiosperms apart is flowers. Flowers are the reproductive organs of flowering plants and their efficiency has led to angiosperms being a successful plant group worldwide.
Angiosperms seem to have an endless variety of flowers, so it might be startling to discover that all flowers only produce one to four of the same basic parts. The parts are sepals, which protect the flower in bud stage, petals, stamens and carpels. If a plant has all four of the parts, it is a complete flower; if not, it's incomplete.
Those wishing to identify the parts in the field find the exercise easier knowing that flower parts always appear in the same order on every flower. Sepals appear on the bottom of the flower between the stem and petals. Petals come next, then the stamens and finally the carpels, center-most of all the parts.
Flowering plants employ sexual reproduction, with flowers serving as the reproductive organs of angiosperms. The stamens and carpels are the specific parts within a flower that contribute sperm and egg, which, if united, end up as a seed that contains an embryonic plant.
Stamens contribute the sperm and are the male parts of flowers. The stamen's top features an anther. The anther produces pollen with sperm inside. Carpels are female structures. The base of the carpel is an ovary that contains eggs ready for fertilization by sperm.
Complete flowers, having both stamens and carpels, are both male and female--they are hermaphrodites. Male flowers are those with only stamens; female flowers lack stamens, boasting carpels, instead.
The plants themselves can be classified according to the sexuality of the flowers, for some plants only have male flowers, others female flowers, and still others have both male and female flowers adorning them. This last kind of flowering plant is called a monoecious plant. Those that are either male or female are dioecious. For dioecious plants to produce seeds, a male and female plant must grow near one another. Plants with hermaphroditic flowers, meanwhile, have no such concern. The hermaphroditic flowers are called "perfect" because they contain everything needed to reproduce.
Flowering plants employ pollinators to get sperm to egg. One pollinator is wind, which blows the pollen to other flowers for fertilization. These flowers are small and not particularly showy. Showier flowers, on the other hand, smell good, look good and provide food in the form of nectar to motivate pollinators to visit. Indeed, flowering plants have evolved to attract preferred pollinators. For instance, tube flowers are geared to let in only pollinators with long beaks--hummingbirds, for instance. Bees see yellow and purple well, so flowers that want to attract bees feature those colors. Flowers that want to attract flies for pollination can smell like rotting flesh.