Fruits are just one part of the reproductive process for plants that produce fruits. Fruits contain seeds and when they go through their natural ripening and rotting process all that will be left of them is the seeds that are left behind. These seeds take root, germinate, and become a new generation of plants. Different fruits have different types of seeds.
Some of them have small clusters of seeds while others only have one or two larger seeds. Some fruits like peaches have a seed that is large and commonly referred to as a pit. Fruits and the seeds inside them are an essential part of the reproductive process that plants that produce fruit go through.