Coconuts reproduce by dropping their fruit on the ground. When the coconut ends up in the ground, in the right environment, it produces a seedling that eventually grows up to become a coconut tree on its own, assuming that the conditions are favorable.
One side of the coconut features a point, and while people and other animals pick up quite a few of the coconuts that fall out of trees, others remain on the ground, and the point eventually is at the lower end of the coconut, thanks to the work of gravity. As cycles of rain and sun continue, and the soil shifts, the coconut eventually ends up with the point below the ground and at least half of the coconut below the level of the soil.
At this point, the growth process starts inside the coconut, and eventually a seedling appears from the top. Over time, the seedling grows, turning into a tree over the course of weeks and months. The coconut tree reproduces in a manner similar to many other fruit trees, dropping the instruments of later generations each time a coconut ends up breaking off from the branches and making the long fall to the ground below.