The function of all flowering plants is to produce seeds. Once the seeds have grown and ripened, the plant has to get them to somewhere that they will be happy growing.

Plants have many ways of spreading or dispersing their seeds.
gravity - heavy seeds will just fall off the plant.
wind - very fine seeds will blow away on the wind. Some seeds have special parachutes or wings to help them fly, for example, dandelions.
hooks - the seeds are covered with hooks which catch on to a passing animals' fur; they then catch a free ride to another place where they are rubbed off later.
animals - the seeds look like tasty treats for the animals to eat, but they pass undigested through the animal. Animals, including birds and insects, sometimes bury the seeds.
pepperpot - the seed-pod is like a little pepperpot and sprinkles the seeds over quite a wide area.
exploding - the seed-pod bursts suddenly, throwing all the seeds out over a large area.
floating - some seeds grow with air trapped in them, so they can float away from the parent plant.