From here:
A fruit is the ripened ovary of a plant, and it holds the plant's seeds. Fruits grow from a plant's flowers, and bananas do all of these things! Banana plants have flowering stems, and when the flowers mature, the ovaries inside them become bananas. In some types of banana, you can see very tiny seeds right in the center of the fruit. But many of the bananas you get at the grocery store are purposefully made to be seedless. Specialty stores sell banana seeds so you can grow your own plants. Banana plantations grow new plants by taking a fleshy bulb called a rhizome or a sucker off an old plant, and then planting the rhizome. I hope that clears everything up about this appealing fruit!