All of these parts help the plant grow big and help to keep the plant healthy. There are a lot of different kinds of plant seeds. Seeds move around before they find a place to grow. The ways that the plants move is seeds can float along water, and some seeds have hooks or stickers and they catch on to animals' fur and fall off later. Another way seeds move is with the wind.
Some plants have seed pods that explode and send all the seeds all over the ground.
Also the seeds spread when animals eat berries and the seeds are left in their droppings. Plants are very interesting things.